Initial commit: AYON Matrix Publish addon

- package.py: addon manifest (v0.1.0)
- server/__init__.py: BaseServerAddon definition
- server/ayon_matrix_publish/plugins/publish/integrate_matrix.py:
  Pyblish plugin that uploads published representations to Matrix
  rooms during the Integration stage. Supports:
  - Upload to Matrix content repository (mxc:// URI)
  - Formatted messages with preview images
  - Auto room creation per asset
  - Configurable via Studio Settings or env vars
- create_package.py: builds distributable .zip package

.gitignore

@@ -0,0 +1,27 @@
+# Python
+__pycache__/
+*.py[cod]
+*.pyo
+*.egg-info/
+dist/
+.eggs/
+
+# Packages
+*.zip
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+
+# Virtualenv
+.venv/
+venv/
+
+# OS
+.DS_Store
+Thumbs.db
+
+# AYON
+*.ayon/