♻️ refactor: migrate 5 bots to KeywordCommandDetector

Migrated to KeywordCommandDetector from @manacore/matrix-bot-common:
- matrix-calendar-bot (termine, kalender keywords)
- matrix-clock-bot (timer, zeit keywords)
- matrix-picture-bot (modelle, verlauf keywords)
- matrix-todo-bot (aufgaben, projekte keywords)
- matrix-zitare-bot (zitat, kategorien keywords)

Removed duplicate KEYWORD_COMMANDS arrays and detectKeywordCommand()
methods from all 5 bots.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

services/matrix-mana-bot/.env.example

@@ -29,3 +29,4 @@ VOICE_BOT_URL=http://localhost:3050
 DEFAULT_VOICE=de-DE-ConradNeural
 DEFAULT_SPEED=1.0
 VOICE_ENABLED=true
+VOICE_PREFERENCES_PATH=./data/voice-preferences.json