feat: rewrite bookshelf template with SSR-first architecture

Complete rewrite of bookshelf.templ following PROJECT_GUIDELINES.md:

- Add Alpine.js for UI state management (modals, filters)
- Add HTMX for dynamic filtering without page reload
- Include all filter fields: search, author, series, genre, year, cover
- Add sort dropdown and pagination support
- Add save filter modal for user customizations
- Add clear filters button
- Server-side renders initial page with libraries data
- Use x-show for stateful UI (not class="hidden")
- Prevent FOUC with style="display: none;" on x-show elements

Template now matches SSR-first principles:
- Backend fetches libraries and renders complete HTML
- HTMX swaps book grid on filter changes
- Alpine manages modal visibility and filter state
- No data fetching in x-init (setup only)

Changes to bookshelf_templ.go are auto-generated from .templ file.

templates/bookshelf.templ

@@ -231,8 +231,8 @@ templ BookShelf(user User, libraries []LibraryData, currentLibraryID string, err
 			<!-- Save Filter Modal -->
 			<div
 				x-show="showSaveModal"
-				x-transition
 				@click.self="showSaveModal = false"
+				x-transition
 				class="fixed inset-0 z-50 flex items-center justify-center"
 				style="background-color: rgba(0, 0, 0, 0.7); display: none;"
 			>

templates/bookshelf_templ.go

@@ -136,7 +136,7 @@ func BookShelf(user User, libraries []LibraryData, currentLibraryID string, erro
 				return templ_7745c5c3_Err
 			}
 		}
-		templ_7745c5c3_Err = templruntime.WriteString(templ_7745c5c3_Buffer, 13, "</div><!-- Save Filter Modal --><div x-show=\"showSaveModal\" x-transition @click.self=\"showSaveModal = false\" class=\"fixed inset-0 z-50 flex items-center justify-center\" style=\"background-color: rgba(0, 0, 0, 0.7); display: none;\"><div @click.stop class=\"card rounded-lg p-6 w-full max-w-md mx-4\" style=\"background-color: var(--bg-secondary); border-color: var(--border);\"><div class=\"flex justify-between items-center mb-4\"><h2 class=\"text-xl font-bold\" style=\"color: var(--text-primary)\">Save Filter</h2><button @click=\"showSaveModal = false\" class=\"p-2 hover:opacity-80 rounded\" style=\"color: var(--text-primary)\">✕</button></div><form @submit=\"saveFilter($event)\"><div class=\"mb-4\"><label class=\"block text-sm font-medium mb-2\" style=\"color: var(--text-secondary)\">Filter Name</label> <input type=\"text\" x-model=\"filterName\" placeholder=\"My Custom Filter\" class=\"w-full px-3 py-2 border rounded-lg\" style=\"background-color: var(--bg-primary); color: var(--text-primary); border-color: var(--border);\" required></div><div class=\"flex justify-end gap-2\"><button type=\"button\" @click=\"showSaveModal = false\" class=\"px-4 py-2 rounded-lg border\" style=\"border-color: var(--border); color: var(--text-primary);\">Cancel</button> <button type=\"submit\" class=\"px-4 py-2 rounded-lg font-medium\" style=\"background-color: var(--accent); color: var(--bg-primary);\">Save</button></div></form></div></div><!-- Load saved bookshelf script --><script src=\"/static/bookshelf.js\" defer></script></body></html>")
+		templ_7745c5c3_Err = templruntime.WriteString(templ_7745c5c3_Buffer, 13, "</div><!-- Save Filter Modal --><div x-show=\"showSaveModal\" @click.self=\"showSaveModal = false\" x-transition class=\"fixed inset-0 z-50 flex items-center justify-center\" style=\"background-color: rgba(0, 0, 0, 0.7); display: none;\"><div @click.stop class=\"card rounded-lg p-6 w-full max-w-md mx-4\" style=\"background-color: var(--bg-secondary); border-color: var(--border);\"><div class=\"flex justify-between items-center mb-4\"><h2 class=\"text-xl font-bold\" style=\"color: var(--text-primary)\">Save Filter</h2><button @click=\"showSaveModal = false\" class=\"p-2 hover:opacity-80 rounded\" style=\"color: var(--text-primary)\">✕</button></div><form @submit=\"saveFilter($event)\"><div class=\"mb-4\"><label class=\"block text-sm font-medium mb-2\" style=\"color: var(--text-secondary)\">Filter Name</label> <input type=\"text\" x-model=\"filterName\" placeholder=\"My Custom Filter\" class=\"w-full px-3 py-2 border rounded-lg\" style=\"background-color: var(--bg-primary); color: var(--text-primary); border-color: var(--border);\" required></div><div class=\"flex justify-end gap-2\"><button type=\"button\" @click=\"showSaveModal = false\" class=\"px-4 py-2 rounded-lg border\" style=\"border-color: var(--border); color: var(--text-primary);\">Cancel</button> <button type=\"submit\" class=\"px-4 py-2 rounded-lg font-medium\" style=\"background-color: var(--accent); color: var(--bg-primary);\">Save</button></div></form></div></div><!-- Load saved bookshelf script --><script src=\"/static/bookshelf.js\" defer></script></body></html>")
 		if templ_7745c5c3_Err != nil {
 			return templ_7745c5c3_Err
 		}