docs: update search API documentation with unified endpoint

- Update search_media_items.md with comprehensive fuzzy filter documentation
- Document all filter parameters (author_filter, series_filter, genre_filter, language_filter)
- Document autocomplete parameters (authors, genres, series, languages)
- Add fuzzy search examples (asimov → Asimov, Isaac)
- Add exact match with quotes examples ("Foundation and Empire")
- Add combined search + filters examples
- Add field-specific search examples for autocomplete
- Document error responses (400, 401, 404)
- Remove deprecated filter_sort_media_items.md (functionality moved to search endpoint)
- Update api-reference.md to reflect unified endpoint
- Update api/api-reference.md to reflect unified endpoint

All text filters use pg_trgm fuzzy matching (threshold: 0.3) except years/booleans which are exact.

docs/developer/api-reference.md

@@ -365,27 +365,6 @@ Authorization: Bearer <token>
 }
 ```
 
-### Filter & Sort Media Items
-
-```http
-GET /api/media-items/filter
-Authorization: Bearer <token>
-Content-Type: application/json
-
-{
-  "library_id": "uuid",
-  "author_filter": "Rowling",
-  "series_filter": "Harry Potter",
-  "genre_filter": "Fantasy",
-  "year_min": 1997,
-  "year_max": 2007,
-  "has_cover": true,
-  "sort": "title ASC",
-  "limit": 20,
-  "offset": 0
-}
-```
-
 ### Update Media Item (Admin Only)
 
 ```http