fix(ci): trigger workflow on main branch to enable :latest tag

Changes:
- Create Gitea workflow for ai-stack-deployer
- Trigger on main branch (default branch)
- Use oussamadouhou + REGISTRY_TOKEN for authentication
- Build from ./Dockerfile

This enables :latest tag creation via {{is_default_branch}}.

Tags created:
- git.app.flexinit.nl/oussamadouhou/ai-stack-deployer:latest
- git.app.flexinit.nl/oussamadouhou/ai-stack-deployer:<sha>

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

.mcp.json

@@ -0,0 +1,9 @@
+{
+  "mcpServers": {
+    "ai-stack-deployer": {
+      "command": "bun",
+      "args": ["run", "src/mcp-server.ts"],
+      "env": {}
+    }
+  }
+}