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/services/translation/base.py

@@ -0,0 +1,26 @@
+"""翻译后端抽象。"""
+from __future__ import annotations
+
+from abc import ABC, abstractmethod
+from dataclasses import dataclass
+
+
+@dataclass
+class TranslationResult:
+    text: str
+    engine: str
+    chars: int
+    cached: bool = False
+
+
+class BaseTranslator(ABC):
+    name: str = "base"
+
+    @abstractmethod
+    async def translate(self, text: str, source: str = "auto", target: str = "zh") -> TranslationResult:
+        """同步调用,失败抛异常。"""
+
+
+def count_chars(s: str) -> int:
+    """近似的字符计数(Unicode 码点)。腾讯 TMT 按字符数计费。"""
+    return len(s)