Add maintenance menu (top-right ⚙) with generate missing PDF thumbnails

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

public/app.mjs

@@ -1940,6 +1940,33 @@ async function init() {
 		btn.addEventListener('click', () => navigate('/' + btn.dataset.section));
 	});
 
+	// Maintenance menu
+	const maint_toggle = document.getElementById('maint-toggle');
+	const maint_dropdown = document.getElementById('maint-dropdown');
+	maint_toggle.addEventListener('click', (e) => {
+		e.stopPropagation();
+		maint_dropdown.hidden = !maint_dropdown.hidden;
+	});
+	document.addEventListener('click', () => { maint_dropdown.hidden = true; });
+
+	document.getElementById('maint-gen-thumbs').addEventListener('click', async () => {
+		maint_dropdown.hidden = true;
+		maint_toggle.textContent = '⏳';
+		maint_toggle.disabled = true;
+		try {
+			const result = await api.maintenance_pdf_thumbs();
+			const refreshed = await api.get_pdfs();
+			all_pdfs = refreshed.pdfs;
+			alert(`Generated ${result.generated} thumbnail(s) of ${result.total} PDF(s).`);
+			render();
+		} catch (err) {
+			alert(`Error: ${err.message}`);
+		} finally {
+			maint_toggle.textContent = '⚙';
+			maint_toggle.disabled = false;
+		}
+	});
+
 	window.addEventListener('popstate', () => { parse_url(); render(); });
 
 	await load_all();