feat(pool,scheduling): 号池调度维度、配额冷却机制与管理后台重构

- 新增 scheduling_dimensions 模块，为每个 Key 计算多维调度状态(手动/冷却/熔断/成本/健康)
- 新增 quota_cooldown 模块，统一判定 Key 的有效冷却原因
- Pool 管理后台 API 扩展 Key 详情字段(调度状态/维度/配额/OAuth 信息)
- 前端 Pool 管理页面重写，支持调度状态展示、批量清理封禁 Key
- Handler 基类增加请求调度元数据采集，stream telemetry 增强
- 请求时间线组件增强，支持 attempted 候选展示
- Kiro OAuth 凭证导入解析改进
- 新增 usage 表 provider_key 索引迁移
- 补充调度维度、配额冷却、候选枚举等单元测试

Closes #197

Co-authored-by: AAEE86 <33052466+AAEE86@users.noreply.github.com>

tests/services/test_aware_scheduler_pool_candidate_enumeration.py

@@ -0,0 +1,57 @@
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+
+from src.services.scheduling.aware_scheduler import CacheAwareScheduler
+
+
+def _mock_key(key_id: str, api_formats: list[str]) -> MagicMock:
+    key = MagicMock()
+    key.id = key_id
+    key.is_active = True
+    key.api_formats = api_formats
+    key.cache_ttl_minutes = 1
+    key.internal_priority = 1
+    return key
+
+
+def _mock_endpoint(api_format: str) -> MagicMock:
+    endpoint = MagicMock()
+    endpoint.id = f"ep_{api_format.lower().replace(':', '_')}"
+    endpoint.is_active = True
+    endpoint.api_format = api_format
+    endpoint.api_family = api_format.split(":", 1)[0]
+    endpoint.endpoint_kind = api_format.split(":", 1)[1]
+    endpoint.format_acceptance_config = None
+    return endpoint
+
+
+@pytest.mark.asyncio
+async def test_pool_provider_enumerates_all_key_candidates() -> None:
+    scheduler = CacheAwareScheduler()
+    builder = scheduler._candidate_builder
+    builder._check_model_support = AsyncMock(return_value=(True, None, None, {"m"}))  # type: ignore[method-assign]
+    builder._check_key_availability = MagicMock(return_value=(True, None, None))  # type: ignore[method-assign]
+
+    provider = MagicMock()
+    provider.id = "p_pool"
+    provider.name = "pool_provider"
+    provider.enable_format_conversion = False
+    provider.config = {"pool_advanced": {}}
+    provider.endpoints = [_mock_endpoint("openai:chat")]
+    provider.api_keys = [
+        _mock_key("k1", ["openai:chat"]),
+        _mock_key("k2", ["openai:chat"]),
+    ]
+
+    candidates = await builder._build_candidates(
+        db=MagicMock(),
+        providers=[provider],
+        client_format="openai:chat",
+        model_name="dummy-model",
+        affinity_key="aff-1",
+        global_conversion_enabled=True,
+    )
+
+    assert len(candidates) == 2
+    assert {str(c.key.id) for c in candidates} == {"k1", "k2"}