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/pipeline.py

@@ -0,0 +1,62 @@
+from datetime import datetime
+from typing import Optional, Dict, Any, List
+from pydantic import BaseModel, Field
+
+
+class PipelineStatsSchema(BaseModel):
+    """Pipeline statistics schema"""
+    total_processed: int = 0
+    success_count: int = 0
+    error_count: int = 0
+    last_run: Optional[datetime] = None
+    average_duration_seconds: Optional[float] = None
+
+
+class PipelineBase(BaseModel):
+    """Base pipeline schema"""
+    name: str = Field(..., min_length=1, max_length=100)
+    type: str = Field(..., description="Type: rss_collector, translator, image_generator")
+    config: Dict[str, Any] = Field(default_factory=dict)
+    schedule: Optional[str] = Field(None, description="Cron expression")
+
+
+class PipelineCreate(PipelineBase):
+    """Schema for creating a new pipeline"""
+    pass
+
+
+class PipelineUpdate(BaseModel):
+    """Schema for updating a pipeline (all fields optional)"""
+    name: Optional[str] = Field(None, min_length=1, max_length=100)
+    status: Optional[str] = Field(None, description="Status: running, stopped, error")
+    config: Optional[Dict[str, Any]] = None
+    schedule: Optional[str] = None
+
+
+class PipelineResponse(PipelineBase):
+    """Schema for pipeline response"""
+    id: str = Field(..., alias="_id")
+    status: str
+    stats: PipelineStatsSchema
+    last_run: Optional[datetime] = None
+    next_run: Optional[datetime] = None
+    created_at: datetime
+    updated_at: datetime
+
+    class Config:
+        populate_by_name = True
+        from_attributes = True
+
+
+class PipelineListResponse(BaseModel):
+    """Schema for pipeline list response"""
+    pipelines: List[PipelineResponse]
+    total: int
+
+
+class PipelineLog(BaseModel):
+    """Schema for pipeline log entry"""
+    timestamp: datetime
+    level: str = Field(..., description="Log level: INFO, WARNING, ERROR")
+    message: str
+    details: Optional[Dict[str, Any]] = None