Integrate Puter AI for Theme Generation and Metadata

[claudemyburgh]

This PR replaces the existing OpenRouter AI integration with Puter AI.

Key changes:

• Backend: App\Services\AiService now points to https://api.puter.com/puterai/openai/v1/chat/completions. It uses the PUTER_AUTH_TOKEN for authentication.
• Frontend: The AiThemeGenerator component now uses the @heyputer/puter.js library directly (puter.ai.chat), enabling a "User-Pays" model where users can use their own Puter credits.
• Configuration: Added PUTER_AUTH_TOKEN, PUTER_MODEL, and VITE_PUTER_MODEL to environment variables.
• Testing: Updated AiDescriptionTest and ThemesControllerTest to fake the Puter API endpoints.
• Dependencies: Added cmdk to package.json to resolve build errors in the registry components.

The build artifacts and logs generated during development have been excluded from this submission to maintain a clean diff.

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PR created automatically by Jules for task 15141914466800440140 started by @claudemyburgh

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