ci(release): change automatic release to manual trigger

- Replace push trigger with workflow_dispatch for manual control
- Add optional version_tag input to override pubspec version
- Add prerelease boolean input for marking releases as pre-release

Author: MasuRii

.github/workflows/release-apk.yml

@@ -1,9 +1,17 @@
 name: Release APK
 
 on:
-  push:
-    branches:
-      - main
+  workflow_dispatch:
+    inputs:
+      version_tag:
+        description: 'Version tag (e.g., v1.0.0). Leave empty to use pubspec.yaml version.'
+        required: false
+        default: ''
+      prerelease:
+        description: 'Mark as prerelease'
+        required: false
+        default: false
+        type: boolean
 
 concurrency:
   group: release-${{ github.ref }}