Fix Android encoding issue and integrate Docker container into PR workflow

1. Replaced non-ASCII '→' character with '->' in `AndroidScreenshotTask.java` to fix `javac` "unmappable character" errors in ASCII-only environments.
2. Migrated `.github/workflows/pr.yml` to run inside the `pr-ci-container` Docker image:
   - Added `packages: read` permission.
   - Configured `JAVA_HOME` using container environment variables (`JAVA_HOME_8`, etc.) instead of `actions/setup-java`.
   - Replaced redundant dependency downloads with local symlinks/copies from `/opt/cn1-binaries`.
   - Removed Java 25 from the build matrix as it's not supported in the container.

Author: google-labs-jules[bot]

Ports/Android/src/com/codename1/impl/android/AndroidScreenshotTask.java

@@ -73,7 +73,7 @@ public void onPixelCopyFinished(int copyResult) {
                     new Handler(Looper.getMainLooper())
             );
         } catch (Throwable t) {
-            // Any unexpected issue → fallback
+            // Any unexpected issue -> fallback
             Log.e(t);
             tryFallbackDraw(w, h);
         }