docs: log network connectivity issue

docs: add Docker cleanup changelog + log network issue (2026-01-31)

docs/incidents/2026-01-31-network-connectivity.md

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+# Network Connectivity Issue
+
+**Date:** 2026-01-31  
+**Status:** OPEN  
+**Severity:** Medium  
+
+## Symptoms
+
+- DNS resolution failing (8.8.8.8 timeout)
+- Cannot connect to local services via 192.168.31.2
+- curl to Gitea (port 3005) returns HTTP 000
+- Git push to Gitea failing
+
+## Affected Services
+
+- Git push to git.xtrm-lab.org
+- Potentially other services using external DNS
+
+## Observations
+
+- Gitea container is running (docker ps confirms)
+- Ports are mapped correctly (0.0.0.0:3005->3000)
+- Internal Docker IP: 172.18.0.31
+- Connections from Unraid shell to local IP timing out
+
+## Possible Causes
+
+- Docker bridge/macvlan network issue
+- iptables/firewall blocking internal traffic
+- VLAN configuration affecting local routing
+- DNS upstream issue
+
+## Workaround
+
+- Pending git commit saved locally: `dbe4699`
+- Push when network is restored: `cd /tmp/infrastructure && git push`
+
+## Next Steps
+
+- [ ] Check iptables rules
+- [ ] Verify Docker network configuration
+- [ ] Check AdGuard DNS upstream settings
+- [ ] Test connectivity from different network paths