refactor(api): TOML 配置 SSOT、统一错误契约、Auth/事务加固与可观测性 (#33)

配置 SSOT（TOML + .env）
统一错误契约
Auth 与事务边界
Redis / Celery 可靠性:业务 Redis（DB/0）与 Celery broker/backend（DB/1）显式拆分；连接池、sync client
可观测性（OpenTelemetry + LGTM）

api/app/core/redis_urls.py

@@ -0,0 +1,96 @@
+"""Redis URL resolution: password injection and Celery DB separation."""
+
+from __future__ import annotations
+
+from urllib.parse import quote, urlparse, urlunparse
+
+
+def _url_has_password(parsed) -> bool:
+    return bool(parsed.password or parsed.username)
+
+
+def inject_redis_password(redis_url: str, password: str | None) -> str:
+    """Inject REDIS_PASSWORD into URL when the URL has no credentials."""
+    if not password:
+        return redis_url
+    parsed = urlparse(redis_url)
+    if _url_has_password(parsed):
+        return redis_url
+    host = parsed.hostname or "localhost"
+    port = parsed.port
+    netloc = f":{quote(password, safe='')}@{host}"
+    if port is not None:
+        netloc = f":{quote(password, safe='')}@{host}:{port}"
+    return urlunparse(
+        (
+            parsed.scheme or "redis",
+            netloc,
+            parsed.path or "",
+            parsed.params,
+            parsed.query,
+            parsed.fragment,
+        )
+    )
+
+
+def _parse_db_index(path: str) -> int:
+    segment = (path or "").strip("/")
+    if not segment:
+        return 0
+    try:
+        return int(segment)
+    except ValueError:
+        return 0
+
+
+def derive_celery_redis_url(
+    redis_url: str,
+    *,
+    celery_redis_url_override: str | None = None,
+) -> str:
+    """Resolve Celery broker/backend URL (override or same host with DB+1).
+
+    Business keys use ``REDIS_URL`` (typically DB/0); Celery broker/backend use
+    the next logical DB. After upgrading to DB separation, unconsumed Celery
+    keys on the business DB are abandoned (one-time cutover).
+
+    When ``REDIS_URL`` uses DB/15, set ``CELERY_REDIS_URL`` explicitly — Redis
+    only supports logical DBs 0–15.
+    """
+    if celery_redis_url_override:
+        return celery_redis_url_override
+    parsed = urlparse(redis_url)
+    db = _parse_db_index(parsed.path)
+    if db >= 15:
+        raise ValueError(
+            "REDIS_URL uses DB/15; Celery cannot auto-derive DB+1. "
+            "Set CELERY_REDIS_URL explicitly."
+        )
+    new_path = f"/{db + 1}"
+    return urlunparse(
+        (
+            parsed.scheme or "redis",
+            parsed.netloc,
+            new_path,
+            parsed.params,
+            parsed.query,
+            parsed.fragment,
+        )
+    )
+
+
+def resolve_redis_urls(
+    redis_url: str,
+    *,
+    redis_password: str | None = None,
+    celery_redis_url_override: str | None = None,
+) -> tuple[str, str]:
+    """Return (business_redis_url, celery_redis_url)."""
+    business = inject_redis_password(redis_url, redis_password)
+    celery = derive_celery_redis_url(
+        business,
+        celery_redis_url_override=celery_redis_url_override,
+    )
+    if celery_redis_url_override is None:
+        celery = inject_redis_password(celery, redis_password)
+    return business, celery