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/TODO.md

@@ -444,9 +444,15 @@ metadata:
 - [x] 프로젝트 구조
 - [x] 기본 설정 (config, database, auth)
 - [x] API 라우터 기본 구조
-- [ ] Pydantic 스키마
+- [x] Pydantic 스키마 (완료 - keyword, pipeline, user, application)
+- [x] MongoDB 데이터 모델 (완료 - keyword, pipeline, user, application)
+- [x] 서비스 레이어 구현 (완료 - KeywordService, PipelineService)
+- [x] Keywords API 완전 구현 (CRUD + stats + toggle)
+- [x] Pipelines API 완전 구현 (CRUD + start/stop/restart + logs + config)
+- [ ] UserService with authentication
+- [ ] ApplicationService
+- [ ] MonitoringService
 - [ ] MongoDB 컬렉션 및 인덱스
-- [ ] 서비스 레이어 구현
 - [ ] Redis 통합
 - [ ] 로그인/인증 API
 - [ ] 에러 핸들링