fix(analytics): 词库单字MySQL预览拒扫+IntegrityError 409+MATCH短语净化

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

yunke-server/app/api/routers/analytics.py

@@ -3,6 +3,7 @@ from __future__ import annotations
 
 from typing import Annotated, Any, Literal
 
+import sqlalchemy as sa
 from fastapi import APIRouter, Depends, HTTPException, Query
 from pydantic import BaseModel
 from sqlalchemy.ext.asyncio import AsyncSession
@@ -107,12 +108,21 @@ async def create_word(session: SessionDep, body: WordIn) -> dict:
         return {"id": w.id, "word": w.word, "enabled": w.enabled}
     except ValueError as exc:
         raise HTTPException(409, str(exc)) from exc
+    except sa.exc.IntegrityError as exc:
+        # 并发撞 word UNIQUE(两请求同词,预检都未见)→ 409,不裸 500。
+        raise HTTPException(409, "词已存在") from exc
 
 
 @router.post("/sensitive/words/preview")
 async def preview_word(session: SessionDep, body: WordPreviewIn) -> dict:
-    """加词前命中量预览(count 为 MySQL 上限语义;warn=超阈值建议收窄)。"""
-    n = await words_svc.preview_count(session, body.word, body.exclude_words)
+    """加词前命中量预览(count 为 MySQL 上限语义;warn=超阈值建议收窄)。
+
+    MySQL 单字词拒扫(400)——LIKE 前导通配全扫 ~16s,加词后从命中列表观察。
+    """
+    try:
+        n = await words_svc.preview_count(session, body.word, body.exclude_words)
+    except ValueError as exc:
+        raise HTTPException(400, str(exc)) from exc
     return {"count": n, "warn": n >= words_svc.PREVIEW_WARN_THRESHOLD}