feat: 풀스택 할일관리 앱 구현 (통합 모달 + 간트차트)

- Backend: FastAPI + MongoDB + Redis (카테고리, 할일 CRUD, 파일 첨부, 검색, 대시보드)
- Frontend: Next.js 15 + Tailwind + React Query + Zustand
- 통합 TodoModal: 생성/수정 모달 통합, 탭 구조 (기본/태그와 첨부)
- 간트차트: 카테고리별 할일 타임라인 시각화
- TodoCard: 제목/카테고리/우선순위/태그/첨부 한줄 표시
- Docker Compose 배포 (Frontend:3010, Backend:8010, MongoDB:27021, Redis:6391)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/main.py

@@ -1,17 +1,55 @@
-from fastapi import FastAPI
-from fastapi.middleware.cors import CORSMiddleware
+from contextlib import asynccontextmanager
 from datetime import datetime
 
-app = FastAPI(title="API", version="1.0.0")
+from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
 
-app.add_middleware(
-    CORSMiddleware,
-    allow_origins=["*"],
-    allow_credentials=True,
-    allow_methods=["*"],
-    allow_headers=["*"],
-)
+from app.config import get_settings
+from app.database import connect_db, disconnect_db
 
-@app.get("/health")
-async def health_check():
-    return {"status": "healthy", "timestamp": datetime.now().isoformat()}
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    """서버 시작/종료 이벤트: MongoDB + Redis 연결 관리"""
+    await connect_db()
+    yield
+    await disconnect_db()
+
+
+def create_app() -> FastAPI:
+    settings = get_settings()
+
+    app = FastAPI(
+        title="todos2 API",
+        description="확장형 할일 관리 애플리케이션 API",
+        version="1.0.0",
+        lifespan=lifespan,
+    )
+
+    # CORS
+    app.add_middleware(
+        CORSMiddleware,
+        allow_origins=["*"],
+        allow_credentials=True,
+        allow_methods=["*"],
+        allow_headers=["*"],
+    )
+
+    # 라우터 등록
+    from app.routers import todos, categories, tags, search, dashboard, uploads
+    app.include_router(todos.router)
+    app.include_router(categories.router)
+    app.include_router(tags.router)
+    app.include_router(search.router)
+    app.include_router(dashboard.router)
+    app.include_router(uploads.router)
+
+    # 헬스 체크
+    @app.get("/health", tags=["health"])
+    async def health_check():
+        return {"status": "healthy", "timestamp": datetime.now().isoformat()}
+
+    return app
+
+
+app = create_app()