Add monochrome icon.

[keymapper-ai]

Closes #2140

Summary

• Added ic_launcher_monochrome.xml — a single-colour vector drawable derived from the existing foreground icon, using android:fillType="evenOdd" so the DPad arrow shapes and keyboard grid appear as transparent cutouts within the two overlapping squares. This gives a clean, recognisable silhouette that Android 13+ can tint with the user's chosen theme colour.
• Updated <adaptive-icon> XML files for the release, debug, and ci build variants (mipmap-anydpi-v26/ic_launcher.xml and ic_launcher_round.xml) to include the new <monochrome> element. The element is silently ignored on Android 12 and below, so there is no backwards-compatibility concern.

Known limitations / areas for human review

• The monochrome drawable is based on the existing foreground paths. If the app icon artwork is updated in the future the monochrome layer should be updated in step.
• The debug and CI build variants have their own foreground drawables; the monochrome layer currently points to the shared base-module drawable, which may differ slightly from those flavour-specific foregrounds. This is an acceptable trade-off for build-only variants that are never distributed.
• Visual verification on a physical Android 13+ device or emulator with a themed icon wallpaper is recommended.

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