feat: implement initial frontend SPA with advanced search, query parsing, and autocomplete suggestions.

backend/main.py

@@ -1455,6 +1455,14 @@ async def api_diagnostics(current_user=Depends(require_admin)):
 if FRONTEND_DIR.exists():
     app.mount("/static", StaticFiles(directory=str(FRONTEND_DIR)), name="static")
 
+    @app.get("/popout/{vault_name}/{path:path}")
+    async def serve_popout(vault_name: str, path: str):
+        """Serve the minimalist popout page for a specific file."""
+        popout_file = FRONTEND_DIR / "popout.html"
+        if popout_file.exists():
+            return HTMLResponse(content=popout_file.read_text(encoding="utf-8"))
+        raise HTTPException(status_code=404, detail="Popout template not found")
+
     @app.get("/{full_path:path}")
     async def serve_spa(full_path: str):
         """Serve the SPA index.html for all non-API routes."""