fix(tunnel): switch protocol QUIC -> http2 for backbone stability

QUIC traffic across CF backbone (esp SIN/BOM POPs to IAD origin)
intermittently fails with 'context canceled' or returns 502. http2
is more stable for cross-region tunneled traffic.

Symptoms reported: 502s for users routed via SIN POP while users
on US/EU POPs got 200s simultaneously.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Zingzy

docker-compose.prod.yml

@@ -35,7 +35,9 @@ services:
     image: cloudflare/cloudflared:latest
     container_name: spoo_tunnel
     restart: always
-    command: tunnel --no-autoupdate run
+    # http2 is more stable than QUIC across CF backbone for cross-region traffic.
+    # SIN/BOM POPs sometimes fail to route to IAD origin via QUIC.
+    command: tunnel --no-autoupdate --protocol http2 run
     environment:
       - TUNNEL_TOKEN=${CF_TUNNEL_TOKEN}
     depends_on: