Fix NavBar sidebar not showing: move all nav CSS to App.vue global styles

Root cause: nav-bar.vue styles compiled with [data-v-xxxxx] attribute
selectors by uni-app Vite plugin, but Vue didn't add the attribute to
DOM elements (styles were not scoped). The CSS selector mismatch meant
no sidebar styles ever applied.

Fix:
- Remove all CSS from nav-bar.vue (<style> block deleted entirely)
- Move ALL nav-bar styles to App.vue's global <style>
- Use .app-wrapper > .nav-bar selector (no data-v issues)
- Mobile: display:none; Desktop (>=1024px): display:flex sidebar
- Also fixed: nav-bar was accidentally visible as block on mobile

uni-app/src/App.vue

@@ -31,8 +31,73 @@ uni-page-body {
   min-height: 100% !important;
 }
 
+/* ===== NavBar — hidden on mobile (uni-app default tab bar is used) ===== */
+.app-wrapper > .nav-bar {
+  display: none;
+}
+
 /* ===== Desktop responsive (≥1024px) ===== */
 @media (min-width: 1024px) {
+  /* NavBar sidebar */
+  .app-wrapper > .nav-bar {
+    display: flex;
+    flex-direction: column;
+    position: fixed;
+    top: 0;
+    left: 0;
+    width: 220px;
+    height: 100vh;
+    background: #fff;
+    box-shadow: 4px 0 16px rgba(0,0,0,0.08);
+    z-index: 999999;
+    border-right: 1px solid #e0e0e0;
+    padding-top: 24px;
+  }
+
+  .nav-brand {
+    font-size: 20px;
+    font-weight: 700;
+    color: #1890ff;
+    padding: 20px 24px 32px;
+    text-align: center;
+  }
+
+  .nav-item {
+    display: flex;
+    flex-direction: row;
+    align-items: center;
+    padding: 14px 24px;
+    margin: 2px 12px;
+    border-radius: 12px;
+    gap: 14px;
+    cursor: pointer;
+    transition: background 0.15s;
+  }
+
+  .nav-item:hover {
+    background: #f0f7ff;
+  }
+
+  .nav-item.active {
+    background: #e6f0ff;
+  }
+
+  .nav-icon {
+    font-size: 22px;
+    line-height: 1;
+    font-family: "Apple Color Emoji", "Segoe UI Emoji", "Noto Color Emoji", sans-serif;
+  }
+
+  .nav-text {
+    font-size: 15px;
+    color: #555;
+  }
+
+  .nav-item.active .nav-text {
+    color: #1890ff;
+    font-weight: 600;
+  }
+
   /* Hide the built-in uni-app tab bar on desktop */
   uni-tabbar {
     display: none !important;