feat(vault): 凭据库（密码+2FA 动态码）与 MASTER_KEY 密钥托管

credentials 表为登录凭据唯一事实源（站点×登录方式，含 oauth/2FA）；账号密码读写重定向凭据层并幂等迁移历史数据；TOTP 按 RFC6238 零依赖自实现，绑定需当前动态码校验；Key Escrow 防 MASTER_KEY 遗失；前端新增凭据库视图与账号 2FA 联动。64 pytest + 16 浏览器端到端验证通过。

app/main.py

@@ -22,7 +22,7 @@ from sqlmodel import Session
 from app.core.config import settings
 from app.core.seed import seed_providers
 from app.database import assets_engine, init_db
-from app.routers import accounts, agent, assets, monitor, notify, providers, ssl, stats, sync
+from app.routers import accounts, agent, assets, credentials, monitor, notify, providers, ssl, stats, sync
 from app.services import cleanup_service
 
 BASE_DIR = Path(__file__).resolve().parent.parent
@@ -112,6 +112,7 @@ app.add_middleware(
 app.include_router(assets.router)
 app.include_router(providers.router)
 app.include_router(accounts.router)
+app.include_router(credentials.router)
 app.include_router(stats.router)
 app.include_router(agent.router)
 app.include_router(monitor.router)