fix(templates): use expression attributes and fix indentation

Convert string-interpolation attributes (value="{ x }") to templ
expression attributes (value={ x }) for IDs, paths, and titles, and
fix indentation in header.templ and progress.templ.

templates/unlinked_books.templ

@@ -49,7 +49,7 @@ templ UnlinkedBooks(user User, unlinkedBooks []UnlinkedBookData) {
 						<div class="card p-6 rounded-lg border" style="background-color: var(--bg-secondary); border-color: var(--border);">
 							<div class="flex gap-6">
 								<div class="flex items-start pt-2">
-									<input type="checkbox" class="unlinked-checkbox w-5 h-5" data-progress-id="{ book.ProgressID }" data-title="{ book.TitleFromDevice }" onchange="updateSelectedCount()"/>
+									<input type="checkbox" class="unlinked-checkbox w-5 h-5" data-progress-id={ book.ProgressID } data-title={ book.TitleFromDevice } onchange="updateSelectedCount()"/>
 								</div>
 								<div class="flex-1">
 									<div class="flex items-center gap-3 mb-4">