Add changelog for initial alpha release

Document initial alpha release and features.

CHANGELOG.md

@@ -0,0 +1,18 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.
+
+## [0.1.0-alpha] - 2026-01-14
+### Added
+- Initial alpha release
+- ownCloud Classic WebDAV backup agent for Home Assistant
+- Backup upload, list, download/restore, and delete via Home Assistant UI
+- Automatic DAV endpoint detection:
+  - `/remote.php/dav/files/<user>/`
+  - `/remote.php/webdav/`
+- Support for app passwords and standard credentials (2FA compatible)
+- Metadata sidecar (`.json`) with fallback listing from `.tar` properties
+- HACS compatible repository structure
+- English UI strings and documentation