Rework Apps tab UI and fix lint issues

- Replace top bar filter icon with inline "Show system apps" checkbox
- Add hint card explaining L/K/Z layer toggles and Zygisk caveat
- Move showSystem state inside AppPickerScreen
- Fix RELEASE_OR_CODENAME lint error (requires API 30, min is 29)
- Mark technical check strings as translatable="false"
- Add Android lint step to CI
- Apply ktlint formatting

.github/workflows/ci.yml

@@ -45,6 +45,8 @@ jobs:
       # Kotlin
       - name: ktlint
         run: ktlint "lsposed/**/*.kt"
+      - name: Android lint
+        run: cd lsposed && ./gradlew --no-daemon :app:lint
 
   kmod:
     runs-on: ubuntu-latest