Update documentation to reflect interactive rating system and API changes

- Update README.md with interactive rating system details
- Document zero-rating behavior in GET /api/ebooks/:id/rating
- Add comprehensive rating system documentation section
- Update Bruno collection files to reflect new API behavior
- Enhance API testing documentation with rating 0 fallback

bruno/README.md

@@ -29,7 +29,7 @@ This directory contains Bruno collection for testing the Bookmann API with compr
 - **Update Reading Progress**: PUT /api/ebooks/:id/progress - Update progress
 
 ### Ratings (Protected - JWT Required)
-- **Get Ebook Rating**: GET /api/ebooks/:id/rating - User's rating for ebook
+- **Get Ebook Rating**: GET /api/ebooks/:id/rating - User's rating for ebook (returns 0 if unrated)
 - **Create/Update Rating**: POST /api/ebooks/:id/rating - Rate ebook (1-5 stars)
 - **Delete Rating**: DELETE /api/ebooks/:id/rating - Remove user's rating
 - **Get All Ratings**: GET /api/ebooks/:id/ratings - All ratings for ebook
@@ -47,7 +47,8 @@ Each request includes:
 
 - **Authentication Flow**: Register → Login → Use Bearer token for all other requests
 - **JWT Tokens**: Valid for 24 hours, include in `Authorization: Bearer <token>` header
-- **User Isolation**: Progress and data are user-specific
+- **User Isolation**: Progress, ratings, and data are user-specific
+- **Rating Behavior**: Get rating returns 0 when no rating exists (instead of 404)
 - **Variables**: Update `ebook_id` for testing specific ebooks
 - **Security**: Passwords hashed with bcrypt, unique email/username constraints
 - **JSON**: All requests/responses use JSON format