fix: increase global rate limit from 100 to 300 req/min

Switching months quickly on received invoices triggered rate limit
due to multiple API calls per navigation.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/server.ts

@@ -58,7 +58,7 @@ async function start() {
   await app.register(cookie);
 
   await app.register(rateLimit, {
-    max: 100,
+    max: 300,
     timeWindow: "1 minute",
   });