feat: 引入 status_snapshot 统一 provider key 状态管理

- 新增 StatusSnapshot 模型，聚合 OAuth / 账号 / 配额三维状态
- 新增 StatusSnapshotStore 负责快照的持久化与查询
- 重构 response_builder / endpoint_models，基于 snapshot 输出状态字段
- 前端抽取 providerKeyStatus / oauthRefreshFeedback 工具函数，
  统一 PoolManagement、ProviderDetailDrawer、BatchDialog 的状态展示
- errorParser 增加已知 OAuth 错误的友好提示
- refresher 适配 snapshot 写入，account_state 扩展状态分类
- 新增 alembic 迁移及存量数据回填脚本
- 补充前后端单元测试

alembic/versions/20260320_1200_c9d8e7f6a5b4_add_status_snapshot_to_provider_api_keys.py

@@ -0,0 +1,41 @@
+"""add status_snapshot column to provider_api_keys
+
+Revision ID: c9d8e7f6a5b4
+Revises: f6e7d8c9b0a1
+Create Date: 2026-03-20 12:00:00.000000
+"""
+
+from __future__ import annotations
+
+from collections.abc import Sequence
+
+import sqlalchemy as sa
+from sqlalchemy import inspect
+
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "c9d8e7f6a5b4"
+down_revision: str | None = "f6e7d8c9b0a1"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
+
+
+def column_exists(table_name: str, column_name: str) -> bool:
+    bind = op.get_bind()
+    inspector = inspect(bind)
+    columns = [c["name"] for c in inspector.get_columns(table_name)]
+    return column_name in columns
+
+
+def upgrade() -> None:
+    if not column_exists("provider_api_keys", "status_snapshot"):
+        op.add_column(
+            "provider_api_keys",
+            sa.Column("status_snapshot", sa.JSON(), nullable=True),
+        )
+
+
+def downgrade() -> None:
+    if column_exists("provider_api_keys", "status_snapshot"):
+        op.drop_column("provider_api_keys", "status_snapshot")