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/app/services/event_bus.py

@@ -81,7 +81,7 @@ class EventBus:
     This class provides:
     - Event publishing to project/agent-specific channels
     - Subscription management for SSE endpoints
-    - Reconnection support via event IDs and sequence numbers
+    - Reconnection support via event IDs (Last-Event-ID)
     - Keepalive messages for connection health
     - Type-safe event creation with the Event schema
 
@@ -108,7 +108,6 @@ class EventBus:
         self._redis_client: redis.Redis | None = None
         self._pubsub: redis.client.PubSub | None = None
         self._connected = False
-        self._sequence_counters: dict[str, int] = {}
 
     @property
     def redis_client(self) -> redis.Redis:
@@ -239,12 +238,6 @@ class EventBus:
         """
         return f"{self.USER_CHANNEL_PREFIX}:{user_id}"
 
-    def _get_next_sequence(self, channel: str) -> int:
-        """Get the next sequence number for a channel's events."""
-        current = self._sequence_counters.get(channel, 0)
-        self._sequence_counters[channel] = current + 1
-        return current + 1
-
     @staticmethod
     def create_event(
         event_type: EventType,