refactor(layout): apply full-width layout to all pages

- Remove max-w-7xl containers from all page templates
- Replace with w-full for full-screen width utilization
- Maintain padding for readability
- Admin templates: modify inner content div only (preserve sidebar layout)

templates/admin_library.templ

@@ -13,7 +13,7 @@ templ AdminLibrary(user User, libraries []LibraryData, users []User) {
 			<div class="flex min-h-screen" style="background-color: var(--bg-primary)">
 			    @AdminSidebar(user, "/admin/library")
 				<main class="flex-1 p-8">
-					<div class="max-w-6xl">
+					<div class="w-full">
 						<div class="mb-8">
 							<div class="flex items-center justify-between mb-4">
 								<a href="/admin" class="btn-secondary px-4 py-2 rounded-lg font-medium">