feat: Add support for streaming of live subscribed events

[duedares-rvj]

Add auth0 event-streams subscribe command for live event streaming.

🔧 Changes

This PR introduces a new command to subscribe to live tenant events via Server-Sent Events (SSE), providing a developer-friendly experience for monitoring Auth0 tenant activity in real-time.

• Smart heartbeat handling: Suppressed by default with periodic "still listening" pulse every 30s; use --show-heartbeats to see all
• Verbose mode (-v): prints full JSON payload after each summary line
• Event filtering (--event-type): subscribe to specific event types only
• Resume support (--from, --from-timestamp): continue from a cursor or timestamp
• File output (--output-file): append raw JSONL for offline analysis
• JSON modes (--json, --json-compact): pipe-friendly output for jq
• Graceful disconnect summary: on Ctrl+C, displays event counts by type and a resume command

📚 References

auth0 event-streams subscribe # Watch all events
auth0 event-streams subscribe --event-type user.updated # Filter by type
auth0 event-streams subscribe -v # Include full payloads
auth0 event-streams subscribe --output-file events.jsonl # Capture for replay
auth0 event-streams subscribe --json | jq '.event.data' # Pipe to jq

🔬 Testing

Manual testing performed for subscribed events. Edge cases addressed with defer operations whenever needed. Eg. File close, stream graceful shutdown etc.