fix: Comprehensive validation and bug fixes

Infrastructure:
- Add Redis and Celery workers to all docker-compose files
- Fix celery migration race condition in entrypoint.sh
- Add healthchecks and resource limits to dev compose
- Update .env.template with Redis/Celery variables

Backend Models & Schemas:
- Rename Sprint.completed_points to velocity (per requirements)
- Add AgentInstance.name as required field
- Rename Issue external tracker fields for consistency
- Add IssueSource and TrackerType enums
- Add Project.default_tracker_type field

Backend Fixes:
- Add Celery retry configuration with exponential backoff
- Remove unused sequence counter from EventBus
- Add mypy overrides for test dependencies
- Fix test file using wrong schema (UserUpdate -> dict)

Frontend Fixes:
- Fix memory leak in useProjectEvents (proper cleanup)
- Fix race condition with stale closure in reconnection
- Sync TokenWithUser type with regenerated API client
- Fix expires_in null handling in useAuth
- Clean up unused imports in prototype pages
- Add ESLint relaxed rules for prototype files

CI/CD:
- Add E2E testing stage with Testcontainers
- Add security scanning with Trivy and pip-audit
- Add dependency caching for faster builds

Tests:
- Update all tests to use renamed fields (velocity, name, etc.)
- Fix 14 schema test failures
- All 1500 tests pass with 91% coverage

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

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

backend/migrate.py

@@ -306,7 +306,7 @@ def show_next_rev_id():
     """Show the next sequential revision ID."""
     next_id = get_next_rev_id()
     print(f"Next revision ID: {next_id}")
-    print(f"\nUsage:")
+    print("\nUsage:")
     print(f"  python migrate.py --local generate 'your_message' --rev-id {next_id}")
     print(f"  python migrate.py --local auto 'your_message' --rev-id {next_id}")
     return next_id
@@ -416,7 +416,7 @@ def main():
     if args.command == 'auto' and offline:
         generate_migration(args.message, rev_id=args.rev_id, offline=True)
         print("\nOffline migration generated. Apply it later with:")
-        print(f"  python migrate.py --local apply")
+        print("  python migrate.py --local apply")
         return
 
     # Setup database URL (must be done before importing settings elsewhere)