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/docker-compose.dev.yml

@@ -31,12 +31,20 @@ services:
     container_name: life-echo-redis-dev
     ports:
       - "48307:6379"
+    environment:
+      REDIS_PASSWORD: ${REDIS_PASSWORD:-}
     volumes:
       - redis_data_dev:/data
-    command: redis-server --appendonly yes
+    command: >
+      sh -c 'exec redis-server --appendonly yes --maxmemory 256mb --maxmemory-policy allkeys-lru
+      $${REDIS_PASSWORD:+--requirepass "$$REDIS_PASSWORD"}'
     restart: unless-stopped
     healthcheck:
-      test: ["CMD", "redis-cli", "ping"]
+      test:
+        [
+          "CMD-SHELL",
+          'if [ -n "$$REDIS_PASSWORD" ]; then redis-cli -a "$$REDIS_PASSWORD" ping | grep -q PONG; else redis-cli ping | grep -q PONG; fi',
+        ]
       interval: 10s
       timeout: 5s
       retries: 5