Introduce Aki throughout the Android app - #39

Introduce Aki, the approved red panda study companion, throughout the Android app: launcher and themed icon, Today, completed quests and session summaries, the deck-list heatmap, both widget styles, AnkiQuest settings, and existing notifications.

The seven original poses ship offline. Encouragement reflects the local collection and current daily profile: finishing one deck does not claim all decks are done, stored freezes alone do not imply protection, and yesterday's cached progress gets neutral wording. Artwork is decorative, messages wrap and follow English/Spanish settings, and notification bitmaps are sampled to a small size. Review weights, scoring, delivery rules, account handling and preference keys are unchanged.

Artwork prompts and usage rules are in docs/branding/aki.md. The companion website and desktop source is prepared separately; it does not add a mobile API dependency.

Validation:

• Kotlin formatting and checks, full Android lint, and the arm64 debug APK build passed locally. Seventy-seven focused tests passed across Aki state/bitmap checks, Home, navigation, widgets, notifier and settings.
• The native Today screen was captured successfully at 320dp in light and dark themes, including 200% font scale. Aki's message wraps and remains readable.
• GitHub checks passed on the final commit: Ubuntu, macOS and Windows unit tests; both Android emulator variants; Kotlin and JavaScript lint; and screenshot comparison. The heatmap test initialization failure on the previous commit was fixed before this final run.