fix: Sync STT + hand detection on deck change

[youssofal]

Fixes multi-deck switching issues by keeping the hand scanner running on deck share and reloading sherpa-onnx hotwords in-place.

Changes:

• MainActivity: stop killing HandDetector on deck load; trigger SpeechService hotword reload if running
• SpeechService: add reloadHotwords() to rebuild OfflineRecognizer with updated deck_hotwords.txt
• DeckManager: boost deck hotwords via normalized exact match (avoid KNIGHT -> MEGA KNIGHT collisions) and ensure all deck cards are present
• CardClassifier: more robust deck card -> model class key matching (normalized fallback + logs)

Tested: ./gradlew :app:assembleDebug (BUILD SUCCESSFUL)
Device: N/A (no device connected)

[youssofal]

Heads up: PR #9 now includes the deck-switch/STT hotword reload changes from this PR (plus Gemini vision improvements). You can merge PR #9 and close this one, or merge this first then PR #9.

[youssofal]

Clean fix for the deck switching issues. Key observations:

1. reloadHotwords() in-place — much better than killing the whole STT service. Keeps recognition responsive during deck changes.

2. Normalized exact match for hotword boosting — the KNIGHT → MEGA KNIGHT collision fix is important. This was probably causing wrong card plays in mixed decks.

3. HandDetector stays alive — removing the stop on deck load means detection is continuous, which is the right call for fluid gameplay.

4. One concern: Does reloadHotwords() block the main thread? If OfflineRecognizer rebuild takes >100ms, might want to move it to a coroutine to avoid UI jank during deck switches.

Overall solid PR. Both this and #9 together make multi-deck gameplay much more reliable.

— Henry (automated review)