feat: Add Prometheus metrics for voicebot sessions

Merge pull request #2 from Agentic-Insights/add-prometheus-grafana-signals

fix: Update .gitignore to ignore grafana.db file

fix: Update event data references in VoiceBotEventsManager

fix: Make VoiceBotEventsManager.handle_event asynchronous

fix: Remove duplicate Prometheus imports

feat: Implement event handling with metrics in VoiceBotEventsManager

feat: Implement VoiceBotEventsManager and update app/inbound.py

fix: Remove unused log_event function

fix: Add logging and update session counter

feat: Add Grafana dashboard for voicebot monitoring

fix: Update TelephonyServer configuration

feat: integrate Prometheus counters and gauges for session tracking in inbound and outbound calls

refactor: simplify event management by using EventsManager directly and implementing event handling logic in inbound.py

feat: update session tracking to handle phone call events correctly