Fetch vrc.tl events via Cloudflare Worker relay

vrc.tl returns 403 for the VPS IP range. Route lookups through a relay
Worker (relay/), configured via vrctl.relayUrl/relaySecret in config.json.
Also handle events without eventSlots/performers instead of crashing.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MrxnVXujrZqNrENxJZfVkU

config.json.example

@@ -6,5 +6,9 @@
 		"clientID": "",
 		"clientSecret": ""
 	},
-	"lfmKey": ""
+	"lfmKey": "",
+	"vrctl": {
+		"relayUrl": "",
+		"relaySecret": ""
+	}
 }