release: v4.8.8 file transfer consent fix

Complete the mandatory receiver-consent gate that was wired in the
backend but never connected to the UI callback chain:

- Add the missing onIncomingFileRequest (4th) callback to
  setFileTransferCallbacks in app.jsx — its absence caused
  handleFileTransferStart to auto-reject every incoming file.
- Remove independent callback registration from FileTransferComponent;
  the component was overwriting app-level callbacks on mount and
  nulling all four on unmount, silently breaking progress/received/
  error handlers whenever the panel was hidden.
- Lift pendingIncomingFiles state to the root component so consent
  prompts are shown regardless of panel visibility; auto-open the
  panel on incoming request.
- Add getReceivedFileObjectURL / revokeReceivedFileObjectURL on
  EnhancedSecureWebRTCManager for download buttons in the panel.
- Update file-transfer-ui-cleanup regression test to match the new
  single-owner callback architecture.
- All 14 tests pass; clean production build.

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

meta.json

@@ -1,10 +1,10 @@
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-  "buildTime": "2026-05-19T13:48:58.703Z",
-  "buildId": "1779198538664-1cc8732",
-  "gitHash": "1cc8732",
+  "version": "1779848383991",
+  "buildVersion": "1779848383991",
+  "appVersion": "4.8.8",
+  "buildTime": "2026-05-27T02:19:44.033Z",
+  "buildId": "1779848383991-2468cb4",
+  "gitHash": "2468cb4",
   "generated": true,
-  "generatedAt": "2026-05-19T13:48:58.704Z"
+  "generatedAt": "2026-05-27T02:19:44.035Z"
 }