docs: clarify sqlc DDL support limitations and correct implementation

**Discovery**: sqlc's DDL support is database-engine specific:

✅ **PostgreSQL**: sqlc generates functions for CREATE INDEX, CREATE FUNCTION
❌ **SQLite**: sqlc does NOT generate CREATE INDEX functions
❌ **Both**: sqlc does NOT generate CREATE TRIGGER functions

**Corrected Implementation**:
- Use sqlc-generated setup functions where available (tables always, PostgreSQL indexes)
- Use manual SQL where sqlc doesn't support (SQLite indexes, all triggers)
- Comments clarify why manual SQL is needed in each case

**Architecture Principle**: Use sqlc for what it supports, supplement with manual SQL for what it doesn't - this is the recommended hybrid approach.

insertr-server/internal/db/database.go

@@ -108,7 +108,7 @@ func (db *Database) initializeSQLiteSchema() error {
 		return fmt.Errorf("failed to create content_versions table: %w", err)
 	}
 
-	// Create indexes (manual for now since sqlc didn't generate them)
+	// Create indexes manually (sqlc doesn't generate CREATE INDEX functions for SQLite)
 	indexQueries := []string{
 		"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);",
@@ -121,7 +121,7 @@ func (db *Database) initializeSQLiteSchema() error {
 		}
 	}
 
-	// Create update trigger (manual for now)
+	// Create update trigger manually (sqlc doesn't generate trigger creation functions)
 	triggerQuery := `
 	CREATE TRIGGER IF NOT EXISTS update_content_updated_at
 	AFTER UPDATE ON content
@@ -141,7 +141,7 @@ func (db *Database) initializeSQLiteSchema() error {
 func (db *Database) initializePostgreSQLSchema() error {
 	ctx := context.Background()
 
-	// Create tables
+	// Create tables using sqlc-generated functions
 	if err := db.postgresqlQueries.InitializeSchema(ctx); err != nil {
 		return fmt.Errorf("failed to create content table: %w", err)
 	}
@@ -150,7 +150,7 @@ func (db *Database) initializePostgreSQLSchema() error {
 		return fmt.Errorf("failed to create content_versions table: %w", err)
 	}
 
-	// Create indexes using generated functions
+	// Create indexes using sqlc-generated functions (PostgreSQL supports this)
 	if err := db.postgresqlQueries.CreateContentSiteIndex(ctx); err != nil {
 		return fmt.Errorf("failed to create content site index: %w", err)
 	}
@@ -163,12 +163,12 @@ func (db *Database) initializePostgreSQLSchema() error {
 		return fmt.Errorf("failed to create versions lookup index: %w", err)
 	}
 
-	// Create update function and trigger
+	// Create update function using sqlc-generated function
 	if err := db.postgresqlQueries.CreateUpdateFunction(ctx); err != nil {
 		return fmt.Errorf("failed to create update function: %w", err)
 	}
 
-	// Create trigger manually (sqlc didn't generate this)
+	// Create trigger manually (sqlc doesn't generate trigger creation functions)
 	triggerQuery := `
 		DROP TRIGGER IF EXISTS update_content_updated_at ON content;
 		CREATE TRIGGER update_content_updated_at