feat: complete HTML-first architecture implementation (Phase 1 & 2)

Major architectural simplification removing content type complexity:

Database Schema:
- Remove 'type' field from content and content_versions tables
- Simplify to pure HTML storage with html_content + original_template
- Regenerate all sqlc models for SQLite and PostgreSQL

API Simplification:
- Remove content type routing and validation
- Eliminate type-specific handlers (text/markdown/structured)
- Unified HTML-first approach for all content operations
- Simplify CreateContent and UpdateContent to HTML-only

Backend Enhancements:
- Update enhancer to only generate data-content-id (no data-content-type)
- Improve container expansion utilities with comprehensive block/inline rules
- Add Phase 3 preparation with boundary-respecting traversal logic
- Strengthen element classification for viable children detection

Documentation:
- Update TODO.md to reflect Phase 1-3 completion status
- Add WORKING_ON.md documenting the architectural transformation
- Mark container expansion and HTML-first architecture as complete

This completes the transition to a unified HTML-first content management system
with automatic style detection and element-based behavior, eliminating the
complex multi-type system in favor of semantic HTML-driven editing.

internal/content/mock.go

@@ -20,15 +20,15 @@ func NewMockClient() *MockClient {
 			ID:          "navbar-logo-2b10ad",
 			SiteID:      "demo",
 			HTMLContent: "Acme Consulting Solutions",
-			Type:        "text",
-			UpdatedAt:   time.Now().Format(time.RFC3339),
+
+			UpdatedAt: time.Now().Format(time.RFC3339),
 		},
 		"navbar-logo-2b10ad-a44bad": {
 			ID:          "navbar-logo-2b10ad-a44bad",
 			SiteID:      "demo",
 			HTMLContent: "Acme Business Advisors",
-			Type:        "text",
-			UpdatedAt:   time.Now().Format(time.RFC3339),
+
+			UpdatedAt: time.Now().Format(time.RFC3339),
 		},
 
 		// Hero Section - index.html (updated with actual IDs)
@@ -36,22 +36,22 @@ func NewMockClient() *MockClient {
 			ID:          "hero-title-7cfeea",
 			SiteID:      "demo",
 			HTMLContent: "Transform Your Business with Strategic Expertise",
-			Type:        "text",
-			UpdatedAt:   time.Now().Format(time.RFC3339),
+
+			UpdatedAt: time.Now().Format(time.RFC3339),
 		},
 		"hero-lead-e47475": {
 			ID:          "hero-lead-e47475",
 			SiteID:      "demo",
 			HTMLContent: "We help <strong>ambitious businesses</strong> grow through strategic planning, process optimization, and digital transformation. Our team brings 20+ years of experience to accelerate your success.",
-			Type:        "text",
-			UpdatedAt:   time.Now().Format(time.RFC3339),
+
+			UpdatedAt: time.Now().Format(time.RFC3339),
 		},
 		"hero-link-76c620": {
 			ID:          "hero-link-76c620",
 			SiteID:      "demo",
 			HTMLContent: "Schedule Free Consultation",
-			Type:        "link",
-			UpdatedAt:   time.Now().Format(time.RFC3339),
+
+			UpdatedAt: time.Now().Format(time.RFC3339),
 		},
 
 		// Hero Section - about.html
@@ -59,15 +59,15 @@ func NewMockClient() *MockClient {
 			ID:          "hero-title-c70343",
 			SiteID:      "demo",
 			HTMLContent: "About Our Consulting Expertise",
-			Type:        "text",
-			UpdatedAt:   time.Now().Format(time.RFC3339),
+
+			UpdatedAt: time.Now().Format(time.RFC3339),
 		},
 		"hero-lead-673026": {
 			ID:          "hero-lead-673026",
 			SiteID:      "demo",
 			HTMLContent: "We're a team of <strong>experienced consultants</strong> dedicated to helping small businesses thrive in today's competitive marketplace through proven strategies.",
-			Type:        "text",
-			UpdatedAt:   time.Now().Format(time.RFC3339),
+
+			UpdatedAt: time.Now().Format(time.RFC3339),
 		},
 
 		// Services Section
@@ -75,15 +75,15 @@ func NewMockClient() *MockClient {
 			ID:          "services-subtitle-c8927c",
 			SiteID:      "demo",
 			HTMLContent: "Our Story",
-			Type:        "text",
-			UpdatedAt:   time.Now().Format(time.RFC3339),
+
+			UpdatedAt: time.Now().Format(time.RFC3339),
 		},
 		"services-text-0d96da": {
 			ID:          "services-text-0d96da",
 			SiteID:      "demo",
 			HTMLContent: "<strong>Founded in 2020</strong>, Acme Consulting emerged from a simple observation: small businesses needed access to the same high-quality strategic advice that large corporations receive, but in a format that was accessible, affordable, and actionable.",
-			Type:        "text",
-			UpdatedAt:   time.Now().Format(time.RFC3339),
+
+			UpdatedAt: time.Now().Format(time.RFC3339),
 		},
 
 		// Default fallback for any missing content
@@ -91,8 +91,8 @@ func NewMockClient() *MockClient {
 			ID:          "default",
 			SiteID:      "demo",
 			HTMLContent: "[Enhanced Content]",
-			Type:        "text",
-			UpdatedAt:   time.Now().Format(time.RFC3339),
+
+			UpdatedAt: time.Now().Format(time.RFC3339),
 		},
 	}
 
@@ -140,20 +140,19 @@ func (m *MockClient) GetAllContent(siteID string) (map[string]engine.ContentItem
 }
 
 // CreateContent creates a new mock content item
-func (m *MockClient) CreateContent(siteID, contentID, htmlContent, originalTemplate, contentType, lastEditedBy string) (*engine.ContentItem, error) {
+func (m *MockClient) CreateContent(siteID, contentID, htmlContent, originalTemplate, lastEditedBy string) (*engine.ContentItem, error) {
 	// For mock client, just create and store the item
 	item := engine.ContentItem{
 		ID:               contentID,
 		SiteID:           siteID,
 		HTMLContent:      htmlContent,
 		OriginalTemplate: originalTemplate,
-		Type:             contentType,
 		UpdatedAt:        time.Now().Format(time.RFC3339),
 		LastEditedBy:     lastEditedBy,
 	}
-	
+
 	// Store in mock data
 	m.data[contentID] = item
-	
+
 	return &item, nil
 }