feat(infra): add Forgejo for self-hosted Git + CI/CD

- Forgejo v11 on port 3041 (git.mana.how via Cloudflare Tunnel)
- Forgejo Runner for CI/CD (GitHub Actions compatible)
- Built-in Docker registry and LFS support
- Registration disabled (admin-only)
- SSH access on port 2222
- Go Services CI workflow (.forgejo/workflows/go-services.yml)
- Setup script: scripts/mac-mini/setup-forgejo.sh

Replaces GitHub dependency for CI/CD. GitHub can remain as
mirror/backup while Forgejo becomes the primary Git host.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cloudflared-config.yml

@@ -18,6 +18,10 @@ ingress:
   - hostname: api.mana.how
     service: http://localhost:3060
 
+  # Forgejo (Git + CI/CD)
+  - hostname: git.mana.how
+    service: http://localhost:3041
+
   # Chat App
   - hostname: chat.mana.how
     service: http://localhost:5010