Rename app from RustDesk to SoonDesk

Changes:
- libs/hbb_common/src/config.rs: APP_NAME = 'SoonDesk' (single source of truth)
- flutter/lib/desktop/widgets/tabbar_widget.dart: hard-coded tab title
- flutter/macos/Runner/Configs/AppInfo.xcconfig: PRODUCT_NAME, BUNDLE_ID
- flutter/macos/Runner.xcodeproj/project.pbxproj: hard-coded BUNDLE_ID override
- flutter/lib/web/bridge.dart: comment about why isCustomClient comparison unchanged

This single APP_NAME change drives:
- Window title (src/ui.rs:87 frame.set_title(&crate::get_app_name()))
- macOS app bundle display name (CFBundleName via $(PRODUCT_NAME))
- Linux .desktop file name
- Config / log directory paths (~/Library/Logs/SoonDesk/)
- Lang translation strings: src/lang.rs auto-replaces 'RustDesk' in all
  translations with APP_NAME when is_rustdesk() returns false (since
  APP_NAME is no longer 'RustDesk').

Protocol-level 'RustDesk' references are preserved (PunchHoleRequest
fields, etc.) so we still interop with upstream RustDesk servers and
clients.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

flutter/lib/desktop/widgets/tabbar_widget.dart

@@ -641,7 +641,7 @@ class _DesktopTabState extends State<DesktopTab>
                         Offstage(
                             offstage: !showTitle,
                             child: const Text(
-                              "RustDesk",
+                              "SoonDesk",
                               style: TextStyle(fontSize: 13),
                             ).marginOnly(left: 2))
                       ]).marginOnly(