What does this PR do?

Adds Canva integration with 8 actions for design automation: create, upload, import, export, and manage designs/assets/folders.

Explain How the Feature Works

OAuth2 authentication with dynamic dropdowns for selecting Canva resources.

Relevant User Scenarios

• Automate design creation and asset management
• Convert documents to Canva designs
• Export designs in multiple formats

Fixes #8135 /claim #8135