fix: resolve JS-005, JS-006, SVC-006 architecture violations

- JS-005: Add initialization guards to email-templates.js (admin/vendor)
- JS-006: Add try/catch error handling to content-pages.js init
- SVC-006: Move db.commit() from services to endpoints for proper
  transaction control in email_template_service and vendor_team_service

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/services/email_template_service.py

@@ -220,7 +220,6 @@ class EmailTemplateService:
         template.body_html = body_html
         template.body_text = body_text
 
-        self.db.commit()
         logger.info(f"Updated platform template: {code}/{language}")
 
     def preview_template(
@@ -575,8 +574,6 @@ class EmailTemplateService:
             name=name,
         )
 
-        self.db.commit()
-
         logger.info(f"Vendor {vendor_id} updated template override: {code}/{language}")
 
         return {
@@ -614,7 +611,6 @@ class EmailTemplateService:
         if not deleted:
             raise ResourceNotFoundException("No override found for this template and language")
 
-        self.db.commit()
         logger.info(f"Vendor {vendor_id} deleted template override: {code}/{language}")
 
     def preview_vendor_template(