feat: provider api_formats 可空继承、OpenAI 图片 edit/variation 与用量配额多项补强

- 鉴权: provider_api_keys.api_formats 改为可空，OAuth 托管 key 自动继承 provider endpoints 激活格式，相关 handler/测试同步更新
- 图片 planner: OpenAI 图片路由新增 edit/variation 操作并完善参数校验、响应合并与流式处理
- 用量: user me usage 返回区分 client_requested_stream/upstream_is_stream，前端 usage 列表筛选与展示增强
- 统计: stats_daily_model 新增 cache_creation_ephemeral_5m/1h tokens 字段与回填链路
- 配额/observability: quota repository 新增内存与 SQL 扩展，admin observability usage 字段扩充
- 其它: OAuth 导入/轮询收敛、provider 汇总与 pool admin 读写链路小修、新增 system_config 缓存与 provider template handler

Closes #318

Co-authored-by: Entropy.Xu <[email protected]>

apps/aether-gateway/src/main.rs

@@ -170,14 +170,14 @@ struct GatewayDataArgs {
     #[arg(
         long,
         env = "AETHER_GATEWAY_DATA_POSTGRES_MAX_CONNECTIONS",
-        default_value_t = 30
+        default_value_t = 100
     )]
     postgres_max_connections: u32,
 
     #[arg(
         long,
         env = "AETHER_GATEWAY_DATA_POSTGRES_ACQUIRE_TIMEOUT_MS",
-        default_value_t = 3_000
+        default_value_t = 10_000
     )]
     postgres_acquire_timeout_ms: u64,
 
@@ -1243,8 +1243,8 @@ mod tests {
                 redis_url: None,
                 redis_key_prefix: None,
                 postgres_min_connections: 1,
-                postgres_max_connections: 30,
-                postgres_acquire_timeout_ms: 3_000,
+                postgres_max_connections: 100,
+                postgres_acquire_timeout_ms: 10_000,
                 postgres_idle_timeout_ms: 60_000,
                 postgres_max_lifetime_ms: 1_800_000,
                 postgres_statement_cache_capacity: 100,