feat: Implement backend core functionality for news-engine-console

Phase 1 Backend Implementation:
- ✅ MongoDB data models (Keyword, Pipeline, User, Application)
- ✅ Pydantic schemas for all models with validation
- ✅ KeywordService: Full CRUD, filtering, pagination, stats, toggle status
- ✅ PipelineService: Full CRUD, start/stop/restart, logs, config management
- ✅ Keywords API: 8 endpoints with complete functionality
- ✅ Pipelines API: 11 endpoints with complete functionality
- ✅ Updated TODO.md to reflect completion

Key Features:
- Async MongoDB operations with Motor
- Comprehensive filtering and pagination support
- Pipeline logging system
- Statistics tracking for keywords and pipelines
- Proper error handling with HTTP status codes
- Type-safe request/response models

Files Added:
- models/: 4 data models with PyObjectId support
- schemas/: 4 schema modules with Create/Update/Response patterns
- services/: KeywordService (234 lines) + PipelineService (332 lines)

Files Modified:
- api/keywords.py: 40 → 212 lines (complete implementation)
- api/pipelines.py: 25 → 300 lines (complete implementation)
- TODO.md: Updated checklist with completed items

Next Steps:
- UserService with authentication
- ApplicationService for OAuth2
- MonitoringService
- Redis integration
- Frontend implementation

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

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

services/news-engine-console/backend/app/schemas/__init__.py

@@ -0,0 +1,44 @@
+# Pydantic Schemas for Request/Response
+from .keyword import (
+    KeywordCreate,
+    KeywordUpdate,
+    KeywordResponse,
+    KeywordListResponse
+)
+from .pipeline import (
+    PipelineCreate,
+    PipelineUpdate,
+    PipelineResponse,
+    PipelineListResponse
+)
+from .user import (
+    UserCreate,
+    UserUpdate,
+    UserResponse,
+    UserLogin,
+    Token
+)
+from .application import (
+    ApplicationCreate,
+    ApplicationUpdate,
+    ApplicationResponse
+)
+
+__all__ = [
+    "KeywordCreate",
+    "KeywordUpdate",
+    "KeywordResponse",
+    "KeywordListResponse",
+    "PipelineCreate",
+    "PipelineUpdate",
+    "PipelineResponse",
+    "PipelineListResponse",
+    "UserCreate",
+    "UserUpdate",
+    "UserResponse",
+    "UserLogin",
+    "Token",
+    "ApplicationCreate",
+    "ApplicationUpdate",
+    "ApplicationResponse",
+]