feat: Add comprehensive shadcn/ui component library

Install 35 shadcn components for standard business application:

Base: Button, Input, Label, Card
Forms: Form, Select, Checkbox, Radio, Switch, Textarea
Auth/Feedback: Dialog, Alert, AlertDialog, Toast, Sonner
Dashboard: Table, Tabs, Avatar, Badge, Dropdown, Popover, Tooltip
Navigation: NavigationMenu, Sidebar, Breadcrumb, Sheet, Command
Data Display: Skeleton, Progress, Separator, ScrollArea, Collapsible,
              Accordion, Pagination

Includes hooks (use-toast, use-mobile) and updated Tailwind config.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/app/globals.css

@@ -25,3 +25,39 @@ body {
     text-wrap: balance;
   }
 }
+
+
+
+@layer base {
+  :root {
+    --sidebar-background: 0 0% 98%;
+    --sidebar-foreground: 240 5.3% 26.1%;
+    --sidebar-primary: 240 5.9% 10%;
+    --sidebar-primary-foreground: 0 0% 98%;
+    --sidebar-accent: 240 4.8% 95.9%;
+    --sidebar-accent-foreground: 240 5.9% 10%;
+    --sidebar-border: 220 13% 91%;
+    --sidebar-ring: 217.2 91.2% 59.8%;
+  }
+  .dark {
+    --sidebar-background: 240 5.9% 10%;
+    --sidebar-foreground: 240 4.8% 95.9%;
+    --sidebar-primary: 224.3 76.3% 48%;
+    --sidebar-primary-foreground: 0 0% 100%;
+    --sidebar-accent: 240 3.7% 15.9%;
+    --sidebar-accent-foreground: 240 4.8% 95.9%;
+    --sidebar-border: 240 3.7% 15.9%;
+    --sidebar-ring: 217.2 91.2% 59.8%;
+  }
+}
+
+
+
+@layer base {
+  * {
+    @apply border-border;
+  }
+  body {
+    @apply bg-background text-foreground;
+  }
+}