Refactor: Replace sidebar with horizontal navigation bar

- Remove sidebar and toggle functionality
- Add Bootstrap navbar with dropdown menus
- Move navigation to top between header and content
- Update menu rendering for Bootstrap dropdowns
- Clean up unused files (header.mustache, sidebar.mustache, sidebar.js)
- Add guide link with book icon in footer
- Simplify layout structure
- Remove duplicate code and fix syntax errors
- Add .gitignore for node_modules and other temp files

engine/assets/css/style.scss

@@ -0,0 +1,246 @@
+// SCSS variables
+$primary: #0d6efd;
+$secondary: #6c757d;
+$success: #198754;
+$info: #0dcaf0;
+$warning: #ffc107;
+$danger: #dc3545;
+$light: #f8f9fa;
+$dark: #212529;
+
+// SCSS mixins
+@mixin transition($properties...) {
+    transition: $properties;
+}
+
+// Custom styles
+* {
+  margin: 0;
+  padding: 0;
+  box-sizing: border-box;
+}
+
+html, body {
+  height: 100%;
+}
+
+body {
+  display: flex;
+  flex-direction: column;
+  min-height: 100vh;
+  position: relative;
+}
+
+.main-wrapper {
+  flex: 1;
+  display: flex;
+  flex-direction: column;
+  min-height: calc(100vh - 70px);
+}
+
+.content-wrapper {
+  flex: 1;
+  display: flex;
+  overflow: hidden;
+}
+
+.sidebar {
+  width: 250px;
+  background-color: #f8f9fa;
+  border-right: 1px solid #dee2e6;
+  overflow-y: auto;
+  flex-shrink: 0;
+  @include transition(transform 0.3s ease);
+  position: fixed;
+  top: 70px;
+  left: 0;
+  height: calc(100vh - 140px);
+  z-index: 999;
+  transform: translateX(0);
+}
+
+.sidebar.collapsed {
+  transform: translateX(-250px);
+}
+
+.sidebar-toggle {
+  position: absolute;
+  top: 15px;
+  right: 15px;
+  z-index: 1001;
+  background: none;
+  border: none;
+  cursor: pointer;
+  @include transition(all 0.3s ease);
+  font-size: 20px;
+  color: #6c757d;
+  width: 30px;
+  height: 30px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  border-radius: 4px;
+  
+  &:hover {
+    color: #0d6efd;
+    background-color: #f8f9fa;
+  }
+}
+
+.sidebar-toggle-outer {
+  position: relative;
+  z-index: 1001;
+  background-color: rgba(255, 255, 255, 0.2);
+  border: 1px solid rgba(255, 255, 255, 0.3);
+  margin-right: 10px;
+  color: white !important;
+  
+  &:hover {
+    background-color: rgba(255, 255, 255, 0.3);
+    color: white !important;
+  }
+}
+
+.sidebar.collapsed .sidebar-toggle-inner {
+  right: auto;
+  left: 15px;
+}
+
+.sidebar.collapsed ~ .main-content {
+  margin-left: 0;
+}
+
+.sidebar.collapsed .sidebar-toggle-outer {
+  display: block !important;
+}
+
+.sidebar:not(.collapsed) .sidebar-toggle-outer {
+  display: none !important;
+}
+
+.main-content {
+  flex: 1;
+  overflow-y: auto;
+  padding: 20px;
+  @include transition(margin-left 0.3s ease);
+  margin-left: 250px;
+}
+
+.folder-toggle {
+  font-weight: bold;
+  color: #212529 !important;
+  cursor: pointer;
+  display: flex;
+  align-items: center;
+  padding: 0.5rem 0.75rem;
+  background-color: #f8f9fa !important;
+  margin: 0.125rem 0;
+  @include transition(background-color 0.2s ease);
+  
+  &:hover {
+    background-color: #e9ecef !important;
+  }
+  
+  &[aria-expanded=true] {
+    background-color: #dee2e6 !important;
+    color: #212529 !important;
+    font-weight: 600;
+  }
+  
+  .arrow {
+    margin-right: 8px;
+    @include transition(transform 0.2s);
+    font-size: 0.8em;
+  }
+  
+  &[aria-expanded=true] .arrow {
+    transform: rotate(90deg);
+  }
+}
+
+.page-link {
+  color: #495057 !important;
+  font-weight: 500;
+  padding: 0.5rem 0.75rem;
+  padding-left: 2rem;
+  background-color: #ffffff !important;
+  margin: 0.125rem 0;
+  @include transition(background-color 0.2s ease);
+  
+  &:hover {
+    color: #212529 !important;
+    background-color: #f8f9fa !important;
+  }
+  
+  &.active {
+    background-color: #0d6efd !important;
+    color: #212529 !important;
+    font-weight: 600;
+  }
+}
+
+.file-info {
+  font-size: 0.9rem;
+  color: #6c757d;
+}
+
+.site-info a {
+  color: #0d6efd;
+  text-decoration: none;
+  
+  &:hover {
+    text-decoration: underline;
+  }
+}
+
+.auto-link {
+  color: #0d6efd;
+  text-decoration: none;
+  border-bottom: 2px dashed #0d6efd;
+  font-weight: 500;
+  @include transition(all 0.2s ease);
+  
+  &:hover {
+    color: #0a58ca;
+    text-decoration: none;
+    border-bottom-style: solid;
+    border-bottom-color: #0a58ca;
+  }
+}
+
+.search-form {
+  max-width: 300px;
+}
+
+.card-title a {
+  text-decoration: none;
+  color: inherit;
+  
+  &:hover {
+    text-decoration: underline;
+  }
+}
+
+.folder-disabled {
+  font-weight: 500;
+  color: #6c757d !important;
+  cursor: not-allowed;
+  display: flex;
+  align-items: center;
+  padding: 0.5rem 0.75rem;
+  background-color: #f8f9fa !important;
+  margin: 0.125rem 0;
+  opacity: 0.7;
+  
+  .arrow {
+    margin-right: 8px;
+    font-size: 0.8em;
+    opacity: 0.6;
+  }
+}
+
+@media (max-width: 768px) {
+  .sidebar {
+    width: 200px;
+  }
+}

engine/assets/favicon.svg

@@ -1,11 +0,0 @@
-<svg width="32" height="32" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg">
-  <!-- < -->
-  <path d="M8 8 L3 16 L8 24" stroke="#ffffff" stroke-width="3" fill="none" stroke-linecap="round" stroke-linejoin="round"/>
-  
-  <!-- / -->
-  <path d="M12 24 L18 8" stroke="#ffffff" stroke-width="3" stroke-linecap="round"/>
-  
-  <!-- .. -->
-  <circle cx="22" cy="20" r="2" fill="#ffffff"/>
-  <circle cx="28" cy="20" r="2" fill="#ffffff"/>
-</svg>

engine/assets/icon.svg

@@ -1,11 +0,0 @@
-<svg width="32" height="32" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg">
-  <!-- < -->
-  <path d="M8 8 L3 16 L8 24" stroke="#ffffff" stroke-width="3" fill="none" stroke-linecap="round" stroke-linejoin="round"/>
-  
-  <!-- / -->
-  <path d="M12 24 L18 8" stroke="#ffffff" stroke-width="3" stroke-linecap="round"/>
-  
-  <!-- .. -->
-  <circle cx="22" cy="20" r="2" fill="#ffffff"/>
-  <circle cx="28" cy="20" r="2" fill="#ffffff"/>
-</svg>