feat: full-text search (messages + customers)

Backend (yunke-server):
- GET /api/search?q=&type=messages|customers|all&channel=&start=&end=&page=&page_size=
  LIKE '%q%' scan over message.text + customer friend_nickname/real_name/
  phone/wechat_phone. type=all returns both sections; each is its own Page[T].
- type=messages orders by timestamp desc; type=customers orders by
  last_chat_time desc (nulls last).
- q required: missing/empty/whitespace -> HTTP 400.
- 14 new tests in tests/test_api_search.py (TDD red -> green).

Frontend (yunkes):
- New /search route + 搜索 nav item with Search icon.
- SearchView.vue: search bar, two stacked sections (消息结果 / 客户结果),
  counts + independent pagination per section, keyword highlighting (escaped),
  click message -> /chat/:channel/:ownerId/:talkerId,
  click customer -> all-fields drawer (CustomerList pattern reuse).
- search() wrapper in src/api/index.ts with SearchQuery/SearchPayload types.
- Empty state: "输入关键词搜索消息和客户".

Co-Authored-By: Claude <noreply@anthropic.com>

yunke-server/app/api/main.py

@@ -16,6 +16,7 @@ Includes:
 * ``GET /api/calls`` (see :mod:`app.api.routers.calls`).
 * ``GET /api/sms`` (see :mod:`app.api.routers.sms`).
 * ``GET /api/sync/status`` (see :mod:`app.api.routers.sync`).
+* ``GET /api/search`` (see :mod:`app.api.routers.search`).
 
 CORS is configured permissively (wildcard origin, no credentials) so the local
 frontend can call the API during development.
@@ -41,6 +42,7 @@ from app.api.routers import (
     media,
     messages,
     organization,
+    search,
     sms,
     sync,
 )
@@ -62,6 +64,7 @@ app.include_router(groups.router)
 app.include_router(calls.router)
 app.include_router(sms.router)
 app.include_router(sync.router)
+app.include_router(search.router)
 
 
 @app.get("/api/health")