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/ram-limits.md

@@ -0,0 +1,42 @@
+---
+title: Configure Memory Limits and Eviction Policies
+impact: HIGH
+impactDescription: Prevents out-of-memory crashes and unpredictable behavior
+tags: memory, maxmemory, eviction, lru, ttl
+description: Configure Memory Limits and Eviction Policies
+alwaysApply: true
+---
+
+## Configure Memory Limits and Eviction Policies
+
+Always configure `maxmemory` and an eviction policy to prevent Redis from consuming all available memory.
+
+**Correct:** Set explicit memory limits.
+
+```
+maxmemory 2gb
+maxmemory-policy allkeys-lru
+```
+
+| Policy | Use Case |
+|--------|----------|
+| `volatile-lru` | Evict keys with TTL, least recently used first |
+| `allkeys-lru` | Evict any key, least recently used first |
+| `volatile-ttl` | Evict keys closest to expiration |
+| `noeviction` | Return errors when memory is full (use for critical data) |
+
+**Incorrect:** Running Redis without memory limits.
+
+```
+# No maxmemory set - Redis will use all available RAM
+# Can cause OOM killer to terminate Redis or other processes
+```
+
+**Memory optimization tips:**
+- Use Hashes for small objects (more memory-efficient than separate keys)
+- Use `OBJECT ENCODING key` to check how Redis stores your data
+- Use `MEMORY USAGE key` to check individual key memory consumption
+- Enable compression in your client for large values
+
+Reference: [Redis Memory Optimization](https://redis.io/docs/latest/operate/oss_and_stack/management/optimization/memory-optimization/)
+