ci: publish multi-arch image to GHCR; move status port to 4733

GitHub Actions builds linux/amd64 and linux/arm64 on every push to main and
pushes a single :latest tag to ghcr.io, so the container can be run without
cloning or building. Tests gate the publish step.

.env.example

@@ -45,7 +45,7 @@ CURRENCY=₹
 
 # ── Runtime ───────────────────────────────────────────────────────────────────
 STATE_PATH=./state.json        # Docker image defaults this to /data/state.json
-PORT=8080                      # status endpoint (--loop mode only)
+PORT=4733                      # status endpoint (--loop mode only)
 
 # Routes only the site checks through a SOCKS5 proxy; notifications stay direct.
 # Needed on datacenter hosts, whose IPs the site's WAF is likely to block.