refactor: replace genre with tags in bookshelf UI

- Add Tags filter input with autocomplete support
- Update datalist from "genre-datalist" to "tags-datalist"
- Update Alpine.js handler from fetchGenreValues to fetchTagValues
- Genre HTML preserved in template comments for future use
- Regenerate template Go files with templ generate

Updates the bookshelf UI to filter by tags instead of genre, matching
the Calibre data model where genre is always NULL but tags are populated.

Relates to IMPLEMENTATION_TAGS_FILTER.md Phase 5

templates/bookshelf.templ

@@ -100,26 +100,44 @@ templ BookShelf(
 							/>
 							<datalist id="author-datalist"></datalist>
 						</div>
-						<!-- Genre Filter with Autocomplete -->
+						<!-- Tags Filter with Autocomplete -->
 						<div class="flex-1 min-w-[150px]">
-							<label class="block text-sm font-medium mb-2" style="color: var(--text-secondary)">
-								Genre
-							</label>
+							<label class="block text-sm font-medium mb-2" style="color: var(--text-secondary)">Tags</label>
 							<input
 								type="text"
-								name="genre_filter"
-								placeholder="Filter by genre"
+								name="tags_filter"
+								placeholder="Filter by tags"
 								class="w-full px-3 py-2 border rounded-lg"
 								style="background-color: var(--bg-primary); color: var(--text-primary); border-color: var(--border);"
 								hx-get="/api/media-items/search"
 								hx-target="#books-grid"
 								hx-trigger="keyup[key=='Enter'] from:#filter-form"
 								hx-include="#filter-form"
-								list="genre-datalist"
-								@input.debounce.300ms="if($el.value.length >= 2) fetchGenreValues($el)"
+								list="tags-datalist"
+								@input.debounce.300ms="if($el.value.length >= 2) fetchTagValues($el)"
 							/>
-							<datalist id="genre-datalist"></datalist>
+							<datalist id="tags-datalist"></datalist>
 						</div>
+						// <!-- Genre Filter with Autocomplete -->
+						// <div class="flex-1 min-w-[150px]">
+						// 	<label class="block text-sm font-medium mb-2" style="color: var(--text-secondary)">
+						// 		Genre
+						// 	</label>
+						// 	<input
+						// 		type="text"
+						// 		name="genre_filter"
+						// 		placeholder="Filter by genre"
+						// 		class="w-full px-3 py-2 border rounded-lg"
+						// 		style="background-color: var(--bg-primary); color: var(--text-primary); border-color: var(--border);"
+						// 		hx-get="/api/media-items/search"
+						// 		hx-target="#books-grid"
+						// 		hx-trigger="keyup[key=='Enter'] from:#filter-form"
+						// 		hx-include="#filter-form"
+						// 		list="genre-datalist"
+						// 		@input.debounce.300ms="if($el.value.length >= 2) fetchGenreValues($el)"
+						// 	/>
+						// 	<datalist id="genre-datalist"></datalist>
+						// </div>
 						<!-- Series Filter with Autocomplete (NEW) -->
 						<div class="flex-1 min-w-[150px]">
 							<label class="block text-sm font-medium mb-2" style="color: var(--text-secondary)">