refactor: consolidate database structure and move injector to engine

Database Structure Cleanup:
- Move all SQL files from ./db/ to ./internal/db/
- Update sqlc.yaml to use new paths (preserving schema+setup.sql hack)
- Consolidate database-related code in single directory
- Remove empty ./db/ directory

Injector Migration:
- Move injector.go from content package to engine package
- Update ContentClient interface to return map instead of slice for GetBulkContent
- Update database client implementation to match interface
- Remove injector dependency from enhancer (stub implementation)

Demo-Site Consolidation:
- Move demo-site to test-sites/demo-site for better organization
- Update build scripts to use new demo-site location
- Maintain all functionality while improving project structure

This continues the unified architecture consolidation by moving core content
processing logic to the engine and organizing related files properly.

internal/content/enhancer.go

@@ -10,8 +10,8 @@ import (
 
 // Enhancer combines parsing and content injection using unified engine
 type Enhancer struct {
-	engine   *engine.ContentEngine
-	injector *Injector
+	engine *engine.ContentEngine
+	// injector functionality will be integrated into engine
 }
 
 // NewEnhancer creates a new HTML enhancer using unified engine
@@ -26,8 +26,7 @@ func NewEnhancer(client ContentClient, siteID string) *Enhancer {
 	}
 
 	return &Enhancer{
-		engine:   engine.NewContentEngine(engineClient),
-		injector: NewInjector(client, siteID),
+		engine: engine.NewContentEngine(engineClient),
 	}
 }
 

internal/db/postgresql/schema.sql

@@ -0,0 +1,42 @@
+-- PostgreSQL-specific schema with BIGINT UNIX timestamps
+-- Main content table (current versions only)
+CREATE TABLE content (
+    id TEXT NOT NULL,
+    site_id TEXT NOT NULL,
+    value TEXT NOT NULL,
+    type TEXT NOT NULL,
+    created_at BIGINT DEFAULT EXTRACT(EPOCH FROM NOW()) NOT NULL,
+    updated_at BIGINT DEFAULT EXTRACT(EPOCH FROM NOW()) NOT NULL,
+    last_edited_by TEXT DEFAULT 'system' NOT NULL,
+    PRIMARY KEY (id, site_id)
+);
+
+-- Version history table for rollback functionality
+CREATE TABLE content_versions (
+    version_id SERIAL PRIMARY KEY,
+    content_id TEXT NOT NULL,
+    site_id TEXT NOT NULL,
+    value TEXT NOT NULL,
+    type TEXT NOT NULL,
+    created_at BIGINT DEFAULT EXTRACT(EPOCH FROM NOW()) NOT NULL,
+    created_by TEXT DEFAULT 'system' NOT NULL
+);
+
+-- Indexes for performance
+CREATE INDEX IF NOT EXISTS idx_content_site_id ON content(site_id);
+CREATE INDEX IF NOT EXISTS idx_content_updated_at ON content(updated_at);
+CREATE INDEX IF NOT EXISTS idx_content_versions_lookup ON content_versions(content_id, site_id, created_at DESC);
+
+-- Function and trigger to automatically update updated_at timestamp
+CREATE OR REPLACE FUNCTION update_updated_at_column()
+RETURNS TRIGGER AS $$
+BEGIN
+    NEW.updated_at = EXTRACT(EPOCH FROM NOW());
+    RETURN NEW;
+END;
+$$ language 'plpgsql';
+
+CREATE TRIGGER update_content_updated_at
+    BEFORE UPDATE ON content
+    FOR EACH ROW
+    EXECUTE FUNCTION update_updated_at_column();

internal/db/postgresql/setup.sql

@@ -0,0 +1,47 @@
+-- name: InitializeSchema :exec
+CREATE TABLE IF NOT EXISTS content (
+    id TEXT NOT NULL,
+    site_id TEXT NOT NULL,
+    value TEXT NOT NULL,
+    type TEXT NOT NULL CHECK (type IN ('text', 'markdown', 'link')),
+    created_at BIGINT DEFAULT (EXTRACT(EPOCH FROM NOW())) NOT NULL,
+    updated_at BIGINT DEFAULT (EXTRACT(EPOCH FROM NOW())) NOT NULL,
+    last_edited_by TEXT DEFAULT 'system' NOT NULL,
+    PRIMARY KEY (id, site_id)
+);
+
+-- name: InitializeVersionsTable :exec
+CREATE TABLE IF NOT EXISTS content_versions (
+    version_id SERIAL PRIMARY KEY,
+    content_id TEXT NOT NULL,
+    site_id TEXT NOT NULL,
+    value TEXT NOT NULL,
+    type TEXT NOT NULL,
+    created_at BIGINT DEFAULT (EXTRACT(EPOCH FROM NOW())) NOT NULL,
+    created_by TEXT DEFAULT 'system' NOT NULL
+);
+
+-- name: CreateContentSiteIndex :exec
+CREATE INDEX IF NOT EXISTS idx_content_site_id ON content(site_id);
+
+-- name: CreateContentUpdatedAtIndex :exec
+CREATE INDEX IF NOT EXISTS idx_content_updated_at ON content(updated_at);
+
+-- name: CreateVersionsLookupIndex :exec
+CREATE INDEX IF NOT EXISTS idx_content_versions_lookup ON content_versions(content_id, site_id, created_at DESC);
+
+-- name: CreateUpdateFunction :exec
+CREATE OR REPLACE FUNCTION update_content_timestamp()
+RETURNS TRIGGER AS $$
+BEGIN
+    NEW.updated_at = EXTRACT(EPOCH FROM NOW());
+    RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+-- name: CreateUpdateTrigger :exec
+DROP TRIGGER IF EXISTS update_content_updated_at ON content;
+CREATE TRIGGER update_content_updated_at
+BEFORE UPDATE ON content
+FOR EACH ROW
+EXECUTE FUNCTION update_content_timestamp();

internal/db/queries/content.sql

@@ -0,0 +1,39 @@
+-- name: GetContent :one
+SELECT id, site_id, value, type, created_at, updated_at, last_edited_by
+FROM content 
+WHERE id = sqlc.arg(id) AND site_id = sqlc.arg(site_id);
+
+-- name: GetAllContent :many
+SELECT id, site_id, value, type, created_at, updated_at, last_edited_by
+FROM content 
+WHERE site_id = sqlc.arg(site_id)
+ORDER BY updated_at DESC;
+
+-- name: GetBulkContent :many
+SELECT id, site_id, value, type, created_at, updated_at, last_edited_by
+FROM content 
+WHERE site_id = sqlc.arg(site_id) AND id IN (sqlc.slice('ids'));
+
+-- name: CreateContent :one
+INSERT INTO content (id, site_id, value, type, last_edited_by)
+VALUES (sqlc.arg(id), sqlc.arg(site_id), sqlc.arg(value), sqlc.arg(type), sqlc.arg(last_edited_by))
+RETURNING id, site_id, value, type, created_at, updated_at, last_edited_by;
+
+-- name: UpdateContent :one
+UPDATE content 
+SET value = sqlc.arg(value), type = sqlc.arg(type), last_edited_by = sqlc.arg(last_edited_by)
+WHERE id = sqlc.arg(id) AND site_id = sqlc.arg(site_id)
+RETURNING id, site_id, value, type, created_at, updated_at, last_edited_by;
+
+-- name: UpsertContent :one
+INSERT INTO content (id, site_id, value, type, last_edited_by)
+VALUES (sqlc.arg(id), sqlc.arg(site_id), sqlc.arg(value), sqlc.arg(type), sqlc.arg(last_edited_by))
+ON CONFLICT(id, site_id) DO UPDATE SET
+    value = EXCLUDED.value,
+    type = EXCLUDED.type,
+    last_edited_by = EXCLUDED.last_edited_by
+RETURNING id, site_id, value, type, created_at, updated_at, last_edited_by;
+
+-- name: DeleteContent :exec
+DELETE FROM content 
+WHERE id = sqlc.arg(id) AND site_id = sqlc.arg(site_id);

internal/db/queries/versions.sql

@@ -0,0 +1,29 @@
+-- name: CreateContentVersion :exec
+INSERT INTO content_versions (content_id, site_id, value, type, created_by)
+VALUES (sqlc.arg(content_id), sqlc.arg(site_id), sqlc.arg(value), sqlc.arg(type), sqlc.arg(created_by));
+
+-- name: GetContentVersionHistory :many
+SELECT version_id, content_id, site_id, value, type, created_at, created_by
+FROM content_versions
+WHERE content_id = sqlc.arg(content_id) AND site_id = sqlc.arg(site_id)
+ORDER BY created_at DESC
+LIMIT sqlc.arg(limit_count);
+
+-- name: GetContentVersion :one
+SELECT version_id, content_id, site_id, value, type, created_at, created_by
+FROM content_versions
+WHERE version_id = sqlc.arg(version_id);
+
+-- name: GetAllVersionsForSite :many
+SELECT 
+    cv.version_id, cv.content_id, cv.site_id, cv.value, cv.type, cv.created_at, cv.created_by,
+    c.value as current_value
+FROM content_versions cv
+LEFT JOIN content c ON cv.content_id = c.id AND cv.site_id = c.site_id
+WHERE cv.site_id = sqlc.arg(site_id)
+ORDER BY cv.created_at DESC
+LIMIT sqlc.arg(limit_count);
+
+-- name: DeleteOldVersions :exec
+DELETE FROM content_versions 
+WHERE created_at < sqlc.arg(created_before) AND site_id = sqlc.arg(site_id);

internal/db/sqlite/schema.sql

@@ -0,0 +1,36 @@
+-- SQLite-specific schema with INTEGER timestamps
+-- Main content table (current versions only)
+CREATE TABLE content (
+    id TEXT NOT NULL,
+    site_id TEXT NOT NULL,
+    value TEXT NOT NULL,
+    type TEXT NOT NULL,
+    created_at INTEGER DEFAULT (strftime('%s', 'now')) NOT NULL,
+    updated_at INTEGER DEFAULT (strftime('%s', 'now')) NOT NULL,
+    last_edited_by TEXT DEFAULT 'system' NOT NULL,
+    PRIMARY KEY (id, site_id)
+);
+
+-- Version history table for rollback functionality
+CREATE TABLE content_versions (
+    version_id INTEGER PRIMARY KEY AUTOINCREMENT,
+    content_id TEXT NOT NULL,
+    site_id TEXT NOT NULL,
+    value TEXT NOT NULL,
+    type TEXT NOT NULL,
+    created_at INTEGER DEFAULT (strftime('%s', 'now')) NOT NULL,
+    created_by TEXT DEFAULT 'system' NOT NULL
+);
+
+-- Indexes for performance
+CREATE INDEX IF NOT EXISTS idx_content_site_id ON content(site_id);
+CREATE INDEX IF NOT EXISTS idx_content_updated_at ON content(updated_at);
+CREATE INDEX IF NOT EXISTS idx_content_versions_lookup ON content_versions(content_id, site_id, created_at DESC);
+
+-- Trigger to automatically update updated_at timestamp
+CREATE TRIGGER IF NOT EXISTS update_content_updated_at
+AFTER UPDATE ON content
+FOR EACH ROW
+BEGIN
+    UPDATE content SET updated_at = strftime('%s', 'now') WHERE id = NEW.id AND site_id = NEW.site_id;
+END;

internal/db/sqlite/setup.sql

@@ -0,0 +1,39 @@
+-- name: InitializeSchema :exec
+CREATE TABLE IF NOT EXISTS content (
+    id TEXT NOT NULL,
+    site_id TEXT NOT NULL,
+    value TEXT NOT NULL,
+    type TEXT NOT NULL CHECK (type IN ('text', 'markdown', 'link')),
+    created_at INTEGER DEFAULT (strftime('%s', 'now')) NOT NULL,
+    updated_at INTEGER DEFAULT (strftime('%s', 'now')) NOT NULL,
+    last_edited_by TEXT DEFAULT 'system' NOT NULL,
+    PRIMARY KEY (id, site_id)
+);
+
+-- name: InitializeVersionsTable :exec
+CREATE TABLE IF NOT EXISTS content_versions (
+    version_id INTEGER PRIMARY KEY AUTOINCREMENT,
+    content_id TEXT NOT NULL,
+    site_id TEXT NOT NULL,
+    value TEXT NOT NULL,
+    type TEXT NOT NULL,
+    created_at INTEGER DEFAULT (strftime('%s', 'now')) NOT NULL,
+    created_by TEXT DEFAULT 'system' NOT NULL
+);
+
+-- name: CreateContentSiteIndex :exec
+CREATE INDEX IF NOT EXISTS idx_content_site_id ON content(site_id);
+
+-- name: CreateContentUpdatedAtIndex :exec
+CREATE INDEX IF NOT EXISTS idx_content_updated_at ON content(updated_at);
+
+-- name: CreateVersionsLookupIndex :exec
+CREATE INDEX IF NOT EXISTS idx_content_versions_lookup ON content_versions(content_id, site_id, created_at DESC);
+
+-- name: CreateUpdateTrigger :exec
+CREATE TRIGGER IF NOT EXISTS update_content_updated_at
+AFTER UPDATE ON content
+FOR EACH ROW
+BEGIN
+    UPDATE content SET updated_at = strftime('%s', 'now') WHERE id = NEW.id AND site_id = NEW.site_id;
+END;

internal/engine/database_client.go

@@ -62,7 +62,7 @@ func (c *DatabaseClient) GetContent(siteID, contentID string) (*ContentItem, err
 }
 
 // GetBulkContent retrieves multiple content items
-func (c *DatabaseClient) GetBulkContent(siteID string, contentIDs []string) ([]*ContentItem, error) {
+func (c *DatabaseClient) GetBulkContent(siteID string, contentIDs []string) (map[string]ContentItem, error) {
 	switch c.database.GetDBType() {
 	case "sqlite3":
 		contents, err := c.database.GetSQLiteQueries().GetBulkContent(context.Background(), sqlite.GetBulkContentParams{
@@ -73,9 +73,9 @@ func (c *DatabaseClient) GetBulkContent(siteID string, contentIDs []string) ([]*
 			return nil, err
 		}
 
-		items := make([]*ContentItem, len(contents))
-		for i, content := range contents {
-			items[i] = &ContentItem{
+		items := make(map[string]ContentItem)
+		for _, content := range contents {
+			items[content.ID] = ContentItem{
 				ID:           content.ID,
 				SiteID:       content.SiteID,
 				Value:        content.Value,
@@ -94,9 +94,9 @@ func (c *DatabaseClient) GetBulkContent(siteID string, contentIDs []string) ([]*
 			return nil, err
 		}
 
-		items := make([]*ContentItem, len(contents))
-		for i, content := range contents {
-			items[i] = &ContentItem{
+		items := make(map[string]ContentItem)
+		for _, content := range contents {
+			items[content.ID] = ContentItem{
 				ID:           content.ID,
 				SiteID:       content.SiteID,
 				Value:        content.Value,

internal/engine/injector.go

@@ -1,4 +1,4 @@
-package content
+package engine
 
 import (
 	"fmt"

internal/engine/types.go

@@ -46,7 +46,7 @@ type ProcessedElement struct {
 // This will be implemented by database clients
 type ContentClient interface {
 	GetContent(siteID, contentID string) (*ContentItem, error)
-	GetBulkContent(siteID string, contentIDs []string) ([]*ContentItem, error)
+	GetBulkContent(siteID string, contentIDs []string) (map[string]ContentItem, error)
 }
 
 // ContentItem represents a piece of content from the database