fix: use rust:slim-trixie for JDK 21 and latest Rust, trim CI paths

- Switch to Debian Trixie base for native JDK 21 and latest Rust
- Remove Adoptium APT repo workaround
- Only trigger Android CI on src-tauri/ and build config changes

.gitea/workflows/android.yml

@@ -5,10 +5,6 @@ on:
     branches: [ master ]
     paths:
       - 'src-tauri/**'
-      - 'src/**'
-      - 'static/**'
-      - 'package.json'
-      - 'pnpm-lock.yaml'
       - 'Dockerfile.android'
       - '.gitea/workflows/android.yml'
   workflow_dispatch: