[Feature Request] Support Cloudflare Workers AI as an additional AI backend

Description Feature Description I would like to propose adding support for Cloudflare Workers AI as an additional AI backend for Paperless-ngx. Motivation Cloudflare Workers AI provides access to a growing collection of LLMs and embedding models through a simple API while offering a strong focus on privacy and cost efficiency. Adding Cloudflare as a provider would give users another option between fully local deployments (e.g. Ollama) and commercial providers such as OpenAI. Benefits Privacy-friendly Many users choose Paperless-ngx specifically to keep their documents under their control. Cloudflare offers a privacy-conscious alternative that may be preferable to sending data to larger AI providers. Free Tier for Home Users Cloudflare Workers AI includes a free usage tier, making AI features accessible for smaller Paperless installations without requiring dedicated GPU hardware. Low Operational Overhead Unlike local AI solutions, users do not need to …