Release 2.7.3.1: harden proxy recovery, updates and local API.

Restore orphaned system proxy after crash, require update SHA-256, add macOS /api auth token, fix UDP ping false positives, HTTPS-only subscriptions, and keep the UI responsive during connect.

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/build-macos-arm64.sh

@@ -59,7 +59,7 @@ build = "${BUILD}"
 full = "${FULL}"
 binp = Path('dist/navis-release/darwin-arm64/Navis')
 h = hashlib.sha256(binp.read_bytes()).hexdigest()
-notes = f"Navis {ver}+{build}: иконка приложения (N), macOS AppIcon; обновление только по кнопке."
+notes = f"Navis {ver}+{build}: восстановление system proxy после crash; auth macOS /api; обязательный SHA обновлений; fix UDP ping; HTTPS-only подписки; UI без зависания на connect."
 for p in [Path('dist/update.json'), Path('dist/navis-release/update.json')]:
     if not p.exists():
         continue