feat(admin): migrate admin UI to Vue3

admin-frontend/src/style.css

@@ -0,0 +1,51 @@
+:root {
+  --app-bg: #f6f7fb;
+  --app-text: #111827;
+  --app-muted: #6b7280;
+  --app-border: rgba(17, 24, 39, 0.08);
+  --app-radius: 12px;
+  --app-shadow: 0 8px 24px rgba(17, 24, 39, 0.06);
+
+  font-family: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI',
+    'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif;
+  font-synthesis: none;
+  text-rendering: optimizeLegibility;
+  -webkit-font-smoothing: antialiased;
+  -moz-osx-font-smoothing: grayscale;
+}
+
+html,
+body,
+#app {
+  height: 100%;
+}
+
+body {
+  margin: 0;
+  background: var(--app-bg);
+  color: var(--app-text);
+}
+
+a {
+  color: inherit;
+  text-decoration: none;
+}
+
+.app-page-title {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 12px;
+  margin: 0 0 12px;
+}
+
+.app-page-title h2 {
+  margin: 0;
+  font-size: 18px;
+  font-weight: 700;
+  letter-spacing: 0.2px;
+}
+
+.app-muted {
+  color: var(--app-muted);
+}