Expose Forgejo publicly at forge.eblu.me (#278)

## Summary

Expose Forgejo publicly at `forge.eblu.me` via the Fly.io reverse proxy — the first dynamic, authenticated public-facing service.

- **Forgejo hardening:** Domain changed to forge.eblu.me, SSH stays on forge.ops.eblu.me, reverse proxy trust headers configured, local registration locked to external-only (Authentik SSO)
- **Tailscale Ingress:** ExternalName Service + Ingress in tailscale-operator creates forge.tail8d86e.ts.net endpoint
- **Fly.io proxy:** nginx server block with rate-limited auth endpoints (3r/s), fail2ban with custom nginx-deny action, security headers, /swagger blocked, WebSocket support, 512m body limit
- **Authentik:** OAuth callback updated to forge.eblu.me
- **DNS/TLS:** CNAME record in Pulumi, cert in fly-setup
- **Rename:** ~29 files updated from forge.ops.eblu.me to forge.eblu.me (HTTPS refs only; SSH, container builds, and Caddy table kept as-is)

## Deployment Order

1. `mise run provision-indri -- --tags forgejo` (config changes)
2. Verify forge.ops.eblu.me still works
3. `argocd app set tailscale-operator --revision feature/forge-public && argocd app sync tailscale-operator`
4. Verify `curl https://forge.tail8d86e.ts.net`
5. `cd fly && fly deploy`
6. Verify pre-DNS: `curl -H "Host: forge.eblu.me" https://blumeops-proxy.fly.dev/`
7. `fly certs add forge.eblu.me -a blumeops-proxy`
8. `argocd app set authentik --revision feature/forge-public && argocd app sync authentik`
9. `mise run dns-preview && mise run dns-up`
10. Full verification (see below)
11. Rehearse `mise run fly-shutoff`
12. After merge: reset ArgoCD revisions to main, re-sync

## Verification Checklist

- [ ] forge.eblu.me loads, shows public repos
- [ ] forge.ops.eblu.me still works from tailnet
- [ ] SSH clone via forge.ops.eblu.me:2222 works
- [ ] HTTPS clone via forge.eblu.me works
- [ ] UI shows forge.eblu.me for HTTPS clone, forge.ops.eblu.me for SSH
- [ ] /swagger returns 403
- [ ] Rapid login attempts trigger 429 rate limit
- [ ] fail2ban bans after 5 failed logins in 10 minutes
- [ ] ArgoCD can still sync (SSH unaffected)
- [ ] `mise run fly-shutoff` stops all public traffic
- [ ] `mise run services-check` passes

Reviewed-on: #278

argocd/manifests/tailscale-operator/kustomization.yaml

@@ -7,5 +7,10 @@ namespace: tailscale
 resources:
   - ../tailscale-operator-base
   - proxygroup-ingress.yaml
-  - egress-forge.yaml
   - external-secret.yaml
+  - svc-forge-external.yaml
+  # endpoints-forge.yaml is NOT managed by ArgoCD — Endpoints are globally
+  # excluded in argocd-cm resource.exclusions (too noisy for auto-managed
+  # Endpoints). Apply manually:
+  #   kubectl --context=minikube-indri apply -f endpoints-forge.yaml
+  - ingress-forge.yaml