feat(search): FTS5 trigram全文索引(中文搜索3.95s→0.003s,1300倍)

- message_fts 外部内容虚拟表+trigram分词(中文子串可MATCH,无需分词库)
- 3个触发器随ORM upsert自动同步索引(抓取器零改动)
- 搜索路由:≥3字走FTS MATCH,<3字/MySQL回退LIKE
- 实测:搜「大众途安」56条,LIKE全扫3.95s→FTS 0.003s;索引+300MB
- 7个新测试(建表幂等/触发器同步/中文匹配/短查询回退/未建索引回退),426绿

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

yunke-server/tests/test_api_search.py

@@ -313,3 +313,45 @@ async def test_customer_pagination(make_client):
     # All seeded phone numbers contain "1" -> all 3.
     assert custs["total"] == 3
     assert len(custs["items"]) == 1
+
+
+# ---------------------------------------------------------------------------
+# FTS 加速路径(2026-08-21): 建了 message_fts 索引时搜索走 trigram MATCH,
+# 结果与 LIKE 一致;未建索引回退 LIKE(现有测试全是这条路径)。
+# ---------------------------------------------------------------------------
+
+async def test_search_uses_fts_when_available(make_client):
+    """建 FTS 索引后 /api/search 结果与 LIKE 等价(中文≥3字)。"""
+    from sqlalchemy.ext.asyncio import async_sessionmaker
+
+    from app.db.fts import ensure_fts
+
+    async def seed(session):
+        await ensure_fts(session)
+        session.add_all([
+            Message(msg_id="f1", channel="wechat", owner_account_id="o", talker_id="t", text="24年大众途安 简约白", timestamp=1000),
+            Message(msg_id="f2", channel="wechat", owner_account_id="o", talker_id="t", text="丰田汉兰达 2958", timestamp=2000),
+        ])
+        await session.commit()
+
+    client = await make_client(seed)
+    r = await client.get("/api/search", params={"q": "大众途安", "type": "messages"})
+    assert r.status_code == 200
+    msgs = r.json()["messages"]
+    assert msgs["total"] == 1
+    assert msgs["items"][0]["msg_id"] == "f1"
+
+
+async def test_search_fts_short_query_falls_back(make_client):
+    """2 字查询(低于 trigram 最小 3 字)回退 LIKE,结果一致。"""
+    from app.db.fts import ensure_fts
+
+    async def seed(session):
+        await ensure_fts(session)
+        session.add(Message(msg_id="s1", channel="wechat", owner_account_id="o", talker_id="t", text="汉兰达", timestamp=1))
+        await session.commit()
+
+    client = await make_client(seed)
+    r = await client.get("/api/search", params={"q": "汉兰", "type": "messages"})
+    assert r.status_code == 200
+    assert r.json()["messages"]["total"] == 1