feat(bridge): separate bridge config from .env, web panel + hot-reload

- BridgeConfigStore: file-backed JSON config (configs/bridge.json)
- Auto-creates config file only when user saves via admin panel
- Hot-reload: watches config file every 5s, reloads adapters live
- Admin API: GET/PUT/DELETE /api/v1/admin/bridge/config/:name
- Frontend: full CRUD page with platform type selector + toggle
- Removed bridge env vars from .env.example

.env.example

@@ -52,19 +52,9 @@ THINK_INTERVAL_SEC=300
 THINK_SILENCE_TIMEOUT_SEC=120
 
 # ---- 平台桥接 ----
-# QQ (OBv11 协议)
-# QQ_OBV11_WS_URL=ws://localhost:3001
-# QQ_ACCESS_TOKEN=
-# QQ_BOT_QQ=
-
-# Telegram
-# TG_BOT_TOKEN=
-
-# Discord
-# DC_BOT_TOKEN=
-
-# Webhook
-# WEBHOOK_LISTEN_ADDR=:9000
+# 桥接配置不在 .env 中管理。
+# 通过 Admin 面板 → 平台桥接 页面进行配置。
+# 配置将保存在 configs/bridge.json，支持热重载。
 
 # ---- 搜索 (SearXNG) ----
 # SEARXNG_URL=http://localhost:8088