feat: initial MVP - FastAPI backend + Vue3 frontend + docker-compose

- backend: FastAPI + SQLAlchemy 2.0(async) + asyncpg + Alembic
- 7 API routes: auth/me/articles/sources/bookmarks/subscriptions/admin
- models: User/Source/Article/Bookmark/Subscription/ApiToken
- services: RSS fetcher (feedparser) + Tencent TMT translator with quota + cache + local NLLB fallback
- workers: APScheduler + asyncio pipeline (fetch -> dedupe -> insert -> translate)
- seed scripts: create_user, seed_sources (5 RSS: Reuters/BBC/Al Jazeera/NHK/DW)
- frontend: Vue 3 + Vite + Naive UI + Pinia + vue-router
- pages: Login, Feed (24h), ArticleDetail, Sources, Bookmarks, AdminSources
- deploy: docker-compose (postgres/redis/api/worker/frontend/caddy)
- docs: README, DEPLOY, architecture, acceptance

backend/app/database.py

@@ -0,0 +1,52 @@
+"""异步 SQLAlchemy 数据库连接。"""
+from __future__ import annotations
+
+from collections.abc import AsyncGenerator
+
+from sqlalchemy.ext.asyncio import (
+    AsyncSession,
+    async_sessionmaker,
+    create_async_engine,
+)
+from sqlalchemy.orm import DeclarativeBase
+
+from app.config import settings
+
+
+class Base(DeclarativeBase):
+    """所有 ORM 模型的基类。"""
+
+
+engine = create_async_engine(
+    settings.database_url,
+    echo=False,
+    pool_size=5,
+    max_overflow=10,
+    pool_pre_ping=True,
+    pool_recycle=1800,
+)
+
+AsyncSessionLocal = async_sessionmaker(
+    bind=engine,
+    class_=AsyncSession,
+    expire_on_commit=False,
+    autoflush=False,
+)
+
+
+async def get_session() -> AsyncGenerator[AsyncSession, None]:
+    """FastAPI 依赖:请求级 session。"""
+    async with AsyncSessionLocal() as session:
+        try:
+            yield session
+        finally:
+            await session.close()
+
+
+async def init_db() -> None:
+    """开发期用,生产请用 alembic。"""
+    # import models to register them
+    from app.models import article, source, user  # noqa: F401
+
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)