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/tests/api/routes/test_events.py

@@ -374,33 +374,6 @@ class TestEventBusUnit:
         assert bus.get_agent_channel(agent_id) == f"agent:{agent_id}"
         assert bus.get_user_channel(user_id) == f"user:{user_id}"
 
-    @pytest.mark.asyncio
-    async def test_event_bus_sequence_counter(self):
-        """Test sequence counter increments."""
-        bus = EventBus()
-        channel = "test-channel"
-
-        seq1 = bus._get_next_sequence(channel)
-        seq2 = bus._get_next_sequence(channel)
-        seq3 = bus._get_next_sequence(channel)
-
-        assert seq1 == 1
-        assert seq2 == 2
-        assert seq3 == 3
-
-    @pytest.mark.asyncio
-    async def test_event_bus_sequence_per_channel(self):
-        """Test sequence counter is per-channel."""
-        bus = EventBus()
-
-        seq1 = bus._get_next_sequence("channel-1")
-        seq2 = bus._get_next_sequence("channel-2")
-        seq3 = bus._get_next_sequence("channel-1")
-
-        assert seq1 == 1
-        assert seq2 == 1  # Different channel starts at 1
-        assert seq3 == 2
-
     def test_event_bus_create_event(self):
         """Test EventBus.create_event factory method."""
         project_id = uuid.uuid4()