Added 60dB integration

[manishEMS47]

60db.ai as a second English TTS provider, alongside ElevenLabs with automatic failover. Across 4 files:

• apiKeys.py — SIXTYDB_API_KEY
• CustomSettings.py — sixtyDB (on/off), ttsProvider (which one to use first), and 60db voice settings (SIXTYDB_VOICE_ID,
  STABILITY, SIMILARITY, SPEED, ENHANCE)
• VoiceAssistant_5.3.py — a 60db TTS call (decodes its base64 audio into textToSpeech.mp3) and a provider chain: chosen provider →
  other provider → offline
• README.md — setup docs

How to use it

1. Put your key in apiKeys.py: SIXTYDB_API_KEY = "your-key"
2. In CustomSettings.py set ttsProvider = "60db" (or "elevenlabs" — the other is the fallback)
3. (Optional) Set SIXTYDB_VOICE_ID from GET https://api.60db.ai/myvoices, or leave it for the default voice
4. Run normally — English now speaks via 60db, Swedish stays on Google TTS