- GET /api/prompts — list all prompts with modified/default flag
- GET /api/prompts/{name} — read prompt content + required variables
- PUT /api/prompts/{name} — save modified prompt with validation
- POST /api/prompts/{name}/reset — restore prompt to default
- Lazy PromptService init to handle lifespan directory creation
- Router registered in main.py before SPA catch-all
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>