refactor: strip AI pipeline to binary photo/other classifier

Drops face recognition, OCR, object detection, and semantic embeddings.
The sole remaining vision task is a CLIP-based binary classifier
(photography vs other); photos in "other" get needs_review=true so
screenshots, documents, memes and scans can be triaged from a new
filter pill in the UI.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/routers/search.py

@@ -25,13 +25,7 @@ class SearchRequest(BaseModel):
 
 @router.post("")
 async def search_photos(body: SearchRequest, db: AsyncSession = Depends(get_db), current_user: User = Depends(get_current_user)):
-    """Unified search endpoint. Every query runs hybrid (FTS + semantic)
-    by default — the user never picks a mode.
-
-    Filters:
-      - tag_ids: list of tag IDs (any kind: user, object, face_cluster)
-      - date_from / date_to: ISO date strings
-    """
+    """FTS search over photo metadata with optional tag and date filters."""
     filters = body.filters or {}
 
     results = await hybrid_search(