Bundle Python and adb so the app needs nothing installed

- app/build/fetch-deps.js downloads a standalone Python 3.12
  (python-build-standalone) for every build and adb from Google's
  platform-tools, pinned by SHA-256, and prunes what the server never
  uses. It replaces the Windows-only embeddable Python.
- The app runs the bundled Python with -I -u -B -X utf8, so a PYTHONHOME
  or PYTHONPATH meant for another Python can't break it and nothing is
  written inside the signed macOS bundle.
- An adb you already have still goes first, so two adb versions don't
  keep restarting each other's server. arm64 Linux has no official
  platform-tools and keeps using the system adb.
- ui/frame_apk.py reads APK badging (package, label, version, min SDK,
  ABIs, icon) from the binary manifest and resources.arsc, replacing
  aapt2. It matches aapt2 on nine F-Droid APKs and finds launcher icons
  the old path missed with adaptive icons.
- The app reads the computer's clipboard through Electron, so Linux no
  longer needs wl-clipboard or xclip.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

.github/workflows/checks.yml

@@ -31,10 +31,10 @@ jobs:
       - name: Server tests
         run: python -m unittest discover -s tests -v
       - name: App syntax
-        run: node --check app/main.js && node --check app/build/make-icon.js && node --check app/build/fetch-python.js
+        run: node --check app/main.js && node --check app/build/make-icon.js && node --check app/build/fetch-deps.js && node --check app/preload.js
 
-  # The server runs on each desktop OS the app ships for. Windows uses the same
-  # Python version the app bundles (app/build/fetch-python.js).
+  # The server runs on each desktop OS the app ships for, on the Python version
+  # the app bundles (app/build/fetch-deps.js) and, on Ubuntu, a newer one.
   server-tests:
     strategy:
       fail-fast: false