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/.agents/skills/redis-development/rules/rqe-dialect.md

@@ -0,0 +1,47 @@
+---
+title: Use DIALECT 2 for Query Syntax
+impact: MEDIUM
+impactDescription: Ensures consistent query behavior and access to modern features
+tags: rqe, dialect, query, syntax
+description: Use DIALECT 2 for Query Syntax
+alwaysApply: true
+---
+
+## Use DIALECT 2 for Query Syntax
+
+Use DIALECT 2 for consistent query behavior. Many Redis client libraries now default to DIALECT 2, and other dialects (1, 3, 4) are deprecated as of Redis 8.
+
+**Correct:** Use DIALECT 2 explicitly or rely on modern client defaults.
+
+```python
+from redis import Redis
+
+r = Redis()
+
+# Modern redis-py (6.0+) defaults to DIALECT 2
+# You can also set it explicitly
+results = r.ft("idx:products").search(
+    "@name:laptop",
+    dialect=2
+)
+```
+
+```
+# In raw commands, specify DIALECT 2
+FT.SEARCH idx:products "@name:laptop" DIALECT 2
+
+FT.AGGREGATE idx:products "@category:{electronics}"
+    GROUPBY 1 @category
+    REDUCE COUNT 0 AS count
+    DIALECT 2
+```
+
+**Note:** DIALECT 2 is required for vector search queries. Most modern client libraries (redis-py 6.0+, go-redis, Lettuce) now use DIALECT 2 by default.
+
+**Why DIALECT 2:**
+- Consistent handling of special characters
+- Better NULL value handling
+- More predictable query parsing
+- Required for vector search
+
+Reference: [Query Dialects](https://redis.io/docs/latest/develop/interact/search-and-query/advanced-concepts/dialects/)