Fix mobile app submodule initialization and cleanup

- Removed incorrect swingmusic_mobile directory
- Properly initialized swingmusic_mobile submodule from swingmusic-mobile.git
- Clean submodule configuration for unified release workflow

swingmusic_mobile/.metadata

@@ -1,45 +0,0 @@
-# This file tracks properties of this Flutter project.
-# Used by Flutter tool to assess capabilities and perform upgrades etc.
-#
-# This file should be version controlled and should not be manually edited.
-
-version:
-  revision: "f6ff1529fd6d8af5f706051d9251ac9231c83407"
-  channel: "stable"
-
-project_type: app
-
-# Tracks metadata for the flutter migrate command
-migration:
-  platforms:
-    - platform: root
-      create_revision: f6ff1529fd6d8af5f706051d9251ac9231c83407
-      base_revision: f6ff1529fd6d8af5f706051d9251ac9231c83407
-    - platform: android
-      create_revision: f6ff1529fd6d8af5f706051d9251ac9231c83407
-      base_revision: f6ff1529fd6d8af5f706051d9251ac9231c83407
-    - platform: ios
-      create_revision: f6ff1529fd6d8af5f706051d9251ac9231c83407
-      base_revision: f6ff1529fd6d8af5f706051d9251ac9231c83407
-    - platform: linux
-      create_revision: f6ff1529fd6d8af5f706051d9251ac9231c83407
-      base_revision: f6ff1529fd6d8af5f706051d9251ac9231c83407
-    - platform: macos
-      create_revision: f6ff1529fd6d8af5f706051d9251ac9231c83407
-      base_revision: f6ff1529fd6d8af5f706051d9251ac9231c83407
-    - platform: web
-      create_revision: f6ff1529fd6d8af5f706051d9251ac9231c83407
-      base_revision: f6ff1529fd6d8af5f706051d9251ac9231c83407
-    - platform: windows
-      create_revision: f6ff1529fd6d8af5f706051d9251ac9231c83407
-      base_revision: f6ff1529fd6d8af5f706051d9251ac9231c83407
-
-  # User provided section
-
-  # List of Local paths (relative to this file) that should be
-  # ignored by the migrate tool.
-  #
-  # Files that are not part of the templates will be ignored by default.
-  unmanaged_files:
-    - 'lib/main.dart'
-    - 'ios/Runner.xcodeproj/project.pbxproj'