docs: Add repository mirroring guide and GitHub Actions

- Complete mirroring guide (GitHub ↔ Gitea)
- GitHub Actions workflow to sync to Gitea
- Mirror status check workflow
- SSH and token authentication methods
- Troubleshooting guide

.github/workflows/sync-to-gitea.yml

@@ -0,0 +1,27 @@
+name: Sync to Gitea
+
+on:
+  push:
+    branches: [main, master]
+  workflow_dispatch:  # Allow manual trigger
+
+jobs:
+  sync:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+        with:
+          fetch-depth: 0  # Full history
+
+      - name: Push to Gitea
+        env:
+          GITEA_TOKEN: ${{ secrets.GITEA_TOKEN }}
+        run: |
+          git remote add gitea https://git.terraphim.cloud/terraphim/gitea-infrastructure.git
+          git config user.name "GitHub Actions"
+          git config user.email "actions@github.com"
+          
+          # Push to Gitea with token authentication
+          # If using HTTPS with token: https://token@url
+          git push https://oauth2:${GITEA_TOKEN}@git.terraphim.cloud/terraphim/gitea-infrastructure.git main