fix: correct tojson|safe usage in templates and update validator

- Remove |safe from |tojson in HTML attributes (x-data) - quotes must
  become " for browsers to parse correctly
- Update LANG-002 and LANG-003 architecture rules to document correct
  |tojson usage patterns:
  - HTML attributes: |tojson (no |safe)
  - Script blocks: |tojson|safe
- Fix validator to warn when |tojson|safe is used in x-data (breaks
  HTML attribute parsing)
- Improve code quality across services, APIs, and tests

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

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

app/api/v1/admin/background_tasks.py

@@ -63,7 +63,9 @@ def _convert_import_to_response(job) -> BackgroundTaskResponse:
         started_at=job.started_at.isoformat() if job.started_at else None,
         completed_at=job.completed_at.isoformat() if job.completed_at else None,
         duration_seconds=duration,
-        description=f"Import from {job.marketplace}: {job.source_url[:50]}..." if len(job.source_url) > 50 else f"Import from {job.marketplace}: {job.source_url}",
+        description=f"Import from {job.marketplace}: {job.source_url[:50]}..."
+        if len(job.source_url) > 50
+        else f"Import from {job.marketplace}: {job.source_url}",
         triggered_by=job.user.username if job.user else None,
         error_message=job.error_message,
         details={
@@ -108,7 +110,9 @@ def _convert_test_run_to_response(run) -> BackgroundTaskResponse:
 @router.get("/tasks", response_model=list[BackgroundTaskResponse])
 async def list_background_tasks(
     status: str | None = Query(None, description="Filter by status"),
-    task_type: str | None = Query(None, description="Filter by type (import, test_run)"),
+    task_type: str | None = Query(
+        None, description="Filter by type (import, test_run)"
+    ),
     limit: int = Query(50, ge=1, le=200),
     db: Session = Depends(get_db),
     current_user: User = Depends(get_current_admin_api),
@@ -122,12 +126,16 @@ async def list_background_tasks(
 
     # Get import jobs
     if task_type is None or task_type == "import":
-        import_jobs = background_tasks_service.get_import_jobs(db, status=status, limit=limit)
+        import_jobs = background_tasks_service.get_import_jobs(
+            db, status=status, limit=limit
+        )
         tasks.extend([_convert_import_to_response(job) for job in import_jobs])
 
     # Get test runs
     if task_type is None or task_type == "test_run":
-        test_runs = background_tasks_service.get_test_runs(db, status=status, limit=limit)
+        test_runs = background_tasks_service.get_test_runs(
+            db, status=status, limit=limit
+        )
         tasks.extend([_convert_test_run_to_response(run) for run in test_runs])
 
     # Sort by start time (most recent first)