Fix navigation: add header to all views, fix back button navigation, add mobile menu to document and editor views

- Document view: Added hamburger menu button and breadcrumb navigation
- Editor view: Added hamburger menu, breadcrumb nav, fixed handleCancel/handleSave
- Editor now navigates to correct parent (project) instead of dashboard
- Mobile menu works on all views (projects, projectView, document, editor)
- Document view back button goes to project (not dashboard)
- Editor cancel/save buttons now go to project or projects list

public/js/views/document.js

@@ -22,6 +22,17 @@ export async function renderDocument(app) {
     }
   };
 
+  // Mobile menu functions
+  window.toggleDocumentMenu = function() {
+    const menu = document.getElementById('document-menu');
+    if (menu) menu.classList.toggle('open');
+  };
+
+  window.closeDocumentMenu = function() {
+    const menu = document.getElementById('document-menu');
+    if (menu) menu.classList.remove('open');
+  };
+
   const appEl = document.getElementById('app');
   
   function render() {
@@ -31,13 +42,31 @@ export async function renderDocument(app) {
 
     appEl.innerHTML = `
       <header class="app-header">
+        <button type="button" class="mobile-nav-btn" onclick="window.toggleDocumentMenu()" title="Menu">☰</button>
         <button type="button" class="btn btn-ghost" onclick="backToProject()">← Back</button>
+        <div class="breadcrumb-nav">
+          <span class="breadcrumb-link" onclick="window.app.navigate('projects')">Projects</span>
+          <span class="breadcrumb-sep">/</span>
+          ${projectId ? `<span class="breadcrumb-link" onclick="window.app.navigate('project', {id: '${projectId}'})">Project</span><span class="breadcrumb-sep">/</span>` : ''}
+          <span class="breadcrumb-current">${escapeHtml(doc.title || 'Document')}</span>
+        </div>
         <div class="header-actions">
-          <button type="button" class="btn btn-ghost" onclick="window.app.navigate('editor', {id: '${doc.id}'})">✏️ Edit</button>
+          <button type="button" class="btn btn-ghost" onclick="window.app.navigate('editor', {id: '${doc.id}', projectId: '${projectId || ''}'})">✏️ Edit</button>
           <button type="button" class="btn btn-ghost" onclick="exportDoc()">📥 Export</button>
           <button type="button" class="btn btn-ghost danger" onclick="deleteDoc()">🗑️ Delete</button>
         </div>
       </header>
+      <div class="mobile-menu" id="document-menu">
+        <div class="mobile-menu-header">
+          <span>Menu</span>
+          <button onclick="window.closeDocumentMenu()">✕</button>
+        </div>
+        <div class="mobile-menu-content">
+          <a href="#" onclick="backToProject(); return false;">← Back to ${projectId ? 'Project' : 'Projects'}</a>
+          <a href="#" onclick="window.app.navigate('editor', {id: '${doc.id}', projectId: '${projectId || ''}'}); window.closeDocumentMenu(); return false;">✏️ Edit Document</a>
+          <a href="#" onclick="window.app.navigate('projects'); window.closeDocumentMenu(); return false;">📋 All Projects</a>
+        </div>
+      </div>
       <main class="main-content">
         <div class="content-body">
           <div class="doc-viewer">