Serve frontends via FastAPI static files to fix Brave browser file access block

Each backend now mounts its frontend directory at /ui/ so the UIs are
accessible via http://localhost:800x/ui/ instead of file:// URLs.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pgvector-demo/backend/main.py

@@ -2,6 +2,7 @@ import os
 from fastapi import FastAPI, Query
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import FileResponse
+from fastapi.staticfiles import StaticFiles
 from dotenv import load_dotenv
 from db import get_connection
 from embedder import embed_text
@@ -10,8 +11,11 @@ load_dotenv()
 
 PHOTOS_DIR = os.getenv("PHOTOS_DIR")
 
+FRONTEND_DIR = os.path.join(os.path.dirname(__file__), "../../pgvector-demo/frontend")
+
 app = FastAPI()
 app.add_middleware(CORSMiddleware, allow_origins=["*"], allow_methods=["*"], allow_headers=["*"])
+app.mount("/ui", StaticFiles(directory=os.path.abspath(FRONTEND_DIR), html=True), name="ui")
 
 @app.get("/search")
 def search(q: str = Query(...), limit: int = Query(12)):