(Tauri/fix):Android APK crashing and UnifiedPush not registering

[TastelessVoid]

Description

Includes some fixes for the Android APK crashing on actual devices and adds missing XML entry for Push Notifications.

Fixes #

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

AI disclosure:

• Partially AI assisted (clarify which code was AI assisted and briefly explain what it does).
• Fully AI generated (explain what all the generated code does in moderate detail).

The proguard rules were adjusted by AI, specifically Cursor, which prevents R8/proguard from stripping/renaming Java symbols which Rust/Tauri/Wry resolve through JNI. This fixes the crash Android APKs experienced on release builds.

While not AI generated the UnifiedPushNotificatons.ts was updated to automatically discover the correct gateway URL depending on provider (similar to Fluffychat does it) and SystemNotification.tsx was updated to store and use the discovered gateway over the configured one.

[hazre]

lgtm