feat(vpn transport): add QUIC transport support with auto fallback to WebSocket

rust/src/ratelimit.rs

@@ -130,10 +130,12 @@ mod tests {
 
     #[test]
     fn tokens_do_not_exceed_burst() {
-        let mut tb = TokenBucket::new(1_000_000, 1_000);
+        // Use a low rate so refill between consecutive calls is negligible
+        let mut tb = TokenBucket::new(100, 1_000);
         // Wait to accumulate — but should cap at burst
         std::thread::sleep(Duration::from_millis(50));
         assert!(tb.try_consume(1_000));
+        // At 100 bytes/sec, the few μs between calls add ~0 tokens
         assert!(!tb.try_consume(1));
     }
 }