Implement distributed synchronization features

- Added a sync manager to handle distributed synchronization across relay peers, initialized in the main application run function.
- Enhanced the event handling to update the serial number for synchronization when events are processed.
- Introduced new API endpoints for synchronization, allowing peers to fetch the current serial number and events within a specified range.
- Implemented peer request validation for synchronization endpoints to ensure authorized access based on NIP-98 authentication.
- Updated configuration to support relay peers for synchronization.
- Bumped version to v0.24.0 to reflect these changes.

app/config/config.go

@@ -50,6 +50,7 @@ type C struct {
 	MonthlyPriceSats    int64         `env:"ORLY_MONTHLY_PRICE_SATS" default:"6000" usage:"price in satoshis for one month subscription (default ~$2 USD)"`
 	RelayURL            string        `env:"ORLY_RELAY_URL" usage:"base URL for the relay dashboard (e.g., https://relay.example.com)"`
 	RelayAddresses      []string      `env:"ORLY_RELAY_ADDRESSES" usage:"comma-separated list of websocket addresses for this relay (e.g., wss://relay.example.com,wss://backup.example.com)"`
+	RelayPeers          []string      `env:"ORLY_RELAY_PEERS" usage:"comma-separated list of peer relay URLs for distributed synchronization (e.g., https://peer1.example.com,https://peer2.example.com)"`
 	FollowListFrequency time.Duration `env:"ORLY_FOLLOW_LIST_FREQUENCY" usage:"how often to fetch admin follow lists (default: 1h)" default:"1h"`
 
 	// Blossom blob storage service level settings