Split chapter-name LLM requests into 100-chapter batches and stream
results back as SSE so large books (e.g. Shadow Slave: 2916 chapters)
never time out or truncate. Frontend shows live batch progress inline
and accumulates proposals as they arrive.
Adds backend handlers and SvelteKit UI for an admin text generation tool.
The tool lets admins propose and apply AI-generated chapter titles and book
descriptions using Cloudflare Workers AI (12 LLM models, model selector shared
across both tabs).