refactor: move record/playback to dedicated page, restore test mode in settings

- New '录制回放' page with sidebar nav entry
- Recording: start/stop/auto, file list with play/export/delete
- Playback: visual bar indicator, opens dashboards to see replayed data
- Settings: restored dev tools section with test mode toggle

server/api.py

@@ -481,11 +481,9 @@ async def api_export_recording(filename: str):
     return FileResponse(path, media_type="application/octet-stream", filename=filename)
 
 
-@router.post("/recording/import")
-async def api_import_recording(file: UploadFile = File(...)):
+@router.delete("/recording/{filename}/delete")
+async def api_delete_recording(filename: str):
     from server.recorder import RECORDINGS_DIR
-    if not file.filename or not file.filename.endswith('.tsr'):
-        raise HTTPException(400, "Only .tsr files are accepted")
-    dest = RECORDINGS_DIR / file.filename
-    dest.write_bytes(await file.read())
+    path = RECORDINGS_DIR / filename
+    if path.exists(): path.unlink()
     return {"ok": True}