Reflect navigation state in URL hash

#all, #type/<id>, #manage-types — back/forward works via popstate,
deep links work on load via apply_hash(location.hash)

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

public/app.mjs

@@ -427,21 +427,21 @@ function render_nav() {
 	const all_btn = document.createElement('button');
 	all_btn.className = 'nav-btn' + (state.active_view === 'entries' && state.active_type === null ? ' active' : '');
 	all_btn.textContent = 'All';
-	all_btn.addEventListener('click', () => { state.active_view = 'entries'; state.active_type = null; render(); });
+	all_btn.addEventListener('click', () => navigate('all'));
 	nav.appendChild(all_btn);
 
 	for (const et of state.entry_types) {
 		const btn = document.createElement('button');
 		btn.className = 'nav-btn' + (state.active_view === 'entries' && state.active_type === et.id ? ' active' : '');
 		btn.textContent = et.title;
-		btn.addEventListener('click', () => { state.active_view = 'entries'; state.active_type = et.id; render(); });
+		btn.addEventListener('click', () => navigate('type/' + et.id));
 		nav.appendChild(btn);
 	}
 
 	const manage_btn = document.createElement('button');
 	manage_btn.className = 'nav-btn' + (state.active_view === 'manage-types' ? ' active' : '');
 	manage_btn.textContent = 'Manage Types';
-	manage_btn.addEventListener('click', () => { state.active_view = 'manage-types'; render(); });
+	manage_btn.addEventListener('click', () => navigate('manage-types'));
 	nav.appendChild(manage_btn);
 }
 
@@ -670,6 +670,34 @@ function render_manage_types(container) {
 	container.appendChild(list);
 }
 
+// ---------------------------------------------------------------------------
+// Routing
+// ---------------------------------------------------------------------------
+
+function apply_hash(hash) {
+	if (hash === 'manage-types') {
+		state.active_view = 'manage-types';
+		state.active_type = null;
+	} else if (hash.startsWith('type/')) {
+		state.active_view = 'entries';
+		state.active_type = hash.slice(5);
+	} else {
+		state.active_view = 'entries';
+		state.active_type = null;
+	}
+}
+
+function navigate(hash) {
+	history.pushState(null, '', '#' + hash);
+	apply_hash(hash);
+	render();
+}
+
+window.addEventListener('popstate', () => {
+	apply_hash(location.hash.slice(1));
+	render();
+});
+
 // ---------------------------------------------------------------------------
 // Main render
 // ---------------------------------------------------------------------------
@@ -755,6 +783,7 @@ async function init() {
 	state.entry_types = types_res.entry_types;
 	state.entries     = entries_res.entries;
 
+	apply_hash(location.hash.slice(1));
 	render();
 }