feat(matrix-mana-bot): add voice input support (Phase 1)

- Add VoiceModule and VoiceService for STT integration
- Override handleAudioMessage to process voice notes
- Transcribe audio via mana-stt (Whisper)
- Route transcribed text through CommandRouter
- Add voice configuration and environment variables
- Update help text and documentation

Voice flow:
1. User sends voice note
2. Bot downloads and transcribes audio
3. Shows transcription: 🎤 *"text"*
4. Routes as normal text command
5. Returns text response

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

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

@@ -22,3 +22,10 @@ CLOCK_API_URL=http://localhost:3017/api/v1
 # Storage paths
 TODO_STORAGE_PATH=./data/todos.json
 CALENDAR_STORAGE_PATH=./data/calendar.json
+
+# Voice Services
+STT_URL=http://localhost:3020
+VOICE_BOT_URL=http://localhost:3050
+DEFAULT_VOICE=de-DE-ConradNeural
+DEFAULT_SPEED=1.0
+VOICE_ENABLED=true