v0.7.0 – Home Assistant Add-on + GHCR Images

• Added Home Assistant add-on packaging (canvas_mcp/ add-on folder + repository metadata)
• Switched add-on to use prebuilt GHCR images (avoids Home Assistant build-context issues)
• Added GitHub Actions workflow to build and publish multi-arch images to GHCR on version tags
• Updated add-on config schema to treat canvas_api_token and mcp_auth_token as password fields
• No changes to Canvas MCP tool behavior (still read-only, Streamable HTTP, optional bearer auth)