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/keyword.py

@@ -0,0 +1,56 @@
+from datetime import datetime
+from typing import Optional, Dict, Any, List
+from pydantic import BaseModel, Field
+
+
+class KeywordBase(BaseModel):
+    """Base keyword schema"""
+    keyword: str = Field(..., min_length=1, max_length=200)
+    category: str = Field(..., description="Category: people, topics, companies")
+    pipeline_type: str = Field(default="all", description="Pipeline type: rss, translation, all")
+    priority: int = Field(default=5, ge=1, le=10)
+    metadata: Dict[str, Any] = Field(default_factory=dict)
+
+
+class KeywordCreate(KeywordBase):
+    """Schema for creating a new keyword"""
+    pass
+
+
+class KeywordUpdate(BaseModel):
+    """Schema for updating a keyword (all fields optional)"""
+    keyword: Optional[str] = Field(None, min_length=1, max_length=200)
+    category: Optional[str] = None
+    status: Optional[str] = Field(None, description="Status: active, inactive")
+    pipeline_type: Optional[str] = None
+    priority: Optional[int] = Field(None, ge=1, le=10)
+    metadata: Optional[Dict[str, Any]] = None
+
+
+class KeywordResponse(KeywordBase):
+    """Schema for keyword response"""
+    id: str = Field(..., alias="_id")
+    status: str
+    created_at: datetime
+    updated_at: datetime
+    created_by: Optional[str] = None
+
+    class Config:
+        populate_by_name = True
+        from_attributes = True
+
+
+class KeywordStats(BaseModel):
+    """Keyword statistics"""
+    total_articles: int = 0
+    articles_last_24h: int = 0
+    articles_last_7d: int = 0
+    last_article_date: Optional[datetime] = None
+
+
+class KeywordListResponse(BaseModel):
+    """Schema for keyword list response"""
+    keywords: List[KeywordResponse]
+    total: int
+    page: int = 1
+    page_size: int = 50