fix(qa): 5 bug fixes — audit dates, CSP, template modal, MITRE sync timeout, data source auto-sync

- audit_service: set timestamp=datetime.now(utc) explicitly so DB never stores NULL
- AuditLogPage: formatDate handles null/undefined timestamps (was showing Jan 1 1970)
- nginx.conf: add CSP script-src hash for inline script (sha256-31OgE8E9...)
- system.py: MITRE sync now runs in BackgroundTasks — returns immediately, no more 120s timeout
- mitre_sync_job.py: add _run_data_sources_sync job (every 6h) that checks sync_frequency
  and auto-syncs overdue enabled data sources
- SystemPage: MITRE sync result shows "started" vs "complete" message
- test-templates.ts: add updateTemplate() API function
- SystemPage: template name cell is now clickable — opens TemplateDetailModal with
  full edit form (name, description, procedure, detection, platform, severity, tool)
  and Save / Activate / Deactivate / Close buttons

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/services/audit_service.py

@@ -58,6 +58,7 @@ def log_action(
         ip_address=ip or None,
         user_agent=ua or None,
         session_id=session_id,
+        timestamp=datetime.now(timezone.utc),
     )
     db.add(entry)
     db.flush()