fix(usage): 抽取 ElapsedTimeText 组件、缩短缓存 TTL 提升实时性，修复 _KeyCandidate slots

- 将 UsageRecordsTable 中的内联计时逻辑抽取为独立的 ElapsedTimeText 组件
- usage records 缓存 TTL 从 15s 降为 3s，全局自动刷新间隔从 5s 改为 3s 并默认开启
- 补充 PoolManager._KeyCandidate 缺失的 __slots__ 字段

src/api/admin/usage/routes.py

@@ -843,7 +843,7 @@ class AdminUsageRecordsAdapter(AdminApiAdapter):
 
     @cache_result(
         key_prefix="admin:usage:records",
-        ttl=CacheTTL.ADMIN_USAGE_RECORDS,
+        ttl=3,  # 使用记录页强调实时性，避免 15s 缓存导致列表滞后
         user_specific=False,
         vary_by=[
             "start_date",

src/api/user_me/routes.py

@@ -771,7 +771,7 @@ class GetUsageAdapter(AuthenticatedApiAdapter):
 
     @cache_result(
         key_prefix="user:usage:records",
-        ttl=CacheTTL.ADMIN_USAGE_RECORDS,
+        ttl=3,  # 使用记录页强调实时性，避免 15s 缓存导致列表滞后
         user_specific=True,
         vary_by=[
             "time_range.start_date",

src/services/provider/pool/manager.py

@@ -302,12 +302,20 @@ class PoolManager:
             )
 
         class _KeyCandidate:
-            __slots__ = ("key", "is_skipped", "skip_reason")
+            __slots__ = (
+                "key",
+                "is_skipped",
+                "skip_reason",
+                "_pool_extra_data",
+                "_pool_scheduling_trace",
+            )
 
             def __init__(self, key: ProviderAPIKey) -> None:
                 self.key = key
                 self.is_skipped = False
                 self.skip_reason: str | None = None
+                self._pool_extra_data: dict | None = None
+                self._pool_scheduling_trace: PoolSchedulingTrace | None = None
 
         wrappers = [_KeyCandidate(k) for k in keys]
         reordered_wrappers = await self.reorder_candidates(session_uuid, wrappers)  # type: ignore[arg-type]