chore: Bump build tooling to Java 21 (#250)

Align local and CI JDK requirements with F-Droid's Java 21 environment to keep builds consistent and avoid tooling mismatch.

.github/workflows/build_on_push.yml

@@ -23,7 +23,7 @@ jobs:
         uses: actions/setup-java@v3
         with:
           distribution: 'temurin'
-          java-version: '17'
+          java-version: '21'
           cache: 'gradle'
       - name: Build with Gradle
         run: |

.github/workflows/release.yml

@@ -17,7 +17,7 @@ jobs:
         uses: actions/setup-java@v3
         with:
           distribution: 'temurin'
-          java-version: '17'
+          java-version: '21'
           cache: 'gradle'
       - name: Inject signing key
         run: |
@@ -51,4 +51,4 @@ jobs:
         uses: shogo82148/actions-upload-release-asset@v1
         with:
           upload_url: ${{ github.event.release.upload_url }}
-          asset_path: ${{ github.workspace }}/app/build/outputs/apk/foss/**/*.apk
+          asset_path: ${{ github.workspace }}/app/build/outputs/apk/foss/**/*.apk

AGENTS.md

@@ -8,7 +8,7 @@ See @.cursor/rules/overview.mdc
 
 ## Build
 
-Requires JDK 17+:
+Requires JDK 21+:
 ```bash
 ./gradlew assemble  # Build APKs
 # Output: app/build/outputs/apk/{flavor}/{debug|release}/Amarok-v{version}+{commit}-{flavor}.apk

app/build.gradle

@@ -95,8 +95,8 @@ android {
     }
 
     compileOptions {
-        sourceCompatibility JavaVersion.VERSION_17
-        targetCompatibility JavaVersion.VERSION_17
+        sourceCompatibility JavaVersion.VERSION_21
+        targetCompatibility JavaVersion.VERSION_21
     }
 
     dependenciesInfo {