refactor: implement unified binary architecture

🏗️ **Major Architecture Refactoring: Separate CLI + Server → Unified Binary**

**Key Changes:**
✅ **Unified Binary**: Single 'insertr' binary with subcommands (enhance, serve)
✅ **Preserved Database Architecture**: Maintained sophisticated sqlc multi-DB setup
✅ **Smart Configuration**: Viper + YAML config with CLI flag precedence
✅ **Updated Build System**: Unified justfile, Air, and npm scripts

**Command Structure:**
- `insertr enhance [input-dir]` - Build-time content injection
- `insertr serve` - HTTP API server (dev + production modes)
- `insertr --config insertr.yaml` - YAML configuration support

**Architecture Benefits:**
- **Shared Database Layer**: Single source of truth for content models
- **Flexible Workflows**: Local DB for dev, remote API for production
- **Simple Deployment**: One binary for all use cases
- **Better UX**: Consistent configuration across build and runtime

**Preserved Features:**
- Multi-database support (SQLite + PostgreSQL)
- sqlc code generation and type safety
- Version control system with rollback
- Professional API endpoints
- Content enhancement pipeline

**Development Workflow:**
- `just dev` - Full-stack development (API server + demo site)
- `just serve` - API server only
- `just enhance` - Build-time content injection
- `air` - Hot reload unified binary

**Migration:** Consolidated insertr-cli/ and insertr-server/ → unified root structure

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 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)
+);
+
+-- 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();

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();

db/queries/content.sql

@@ -0,0 +1,30 @@
+-- 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: DeleteContent :exec
+DELETE FROM content 
+WHERE id = sqlc.arg(id) AND site_id = sqlc.arg(site_id);

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);

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 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)
+);
+
+-- 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;

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;