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>

tailwind.config.ts

@@ -1,18 +1,51 @@
 import type { Config } from "tailwindcss";
 
 const config: Config = {
-  content: [
+    darkMode: ["class"],
+    content: [
     "./src/pages/**/*.{js,ts,jsx,tsx,mdx}",
     "./src/components/**/*.{js,ts,jsx,tsx,mdx}",
     "./src/app/**/*.{js,ts,jsx,tsx,mdx}",
   ],
   theme: {
-    extend: {
-      colors: {
-        background: "var(--background)",
-        foreground: "var(--foreground)",
-      },
-    },
+  	extend: {
+  		colors: {
+  			background: 'var(--background)',
+  			foreground: 'var(--foreground)',
+  			sidebar: {
+  				DEFAULT: 'hsl(var(--sidebar-background))',
+  				foreground: 'hsl(var(--sidebar-foreground))',
+  				primary: 'hsl(var(--sidebar-primary))',
+  				'primary-foreground': 'hsl(var(--sidebar-primary-foreground))',
+  				accent: 'hsl(var(--sidebar-accent))',
+  				'accent-foreground': 'hsl(var(--sidebar-accent-foreground))',
+  				border: 'hsl(var(--sidebar-border))',
+  				ring: 'hsl(var(--sidebar-ring))'
+  			}
+  		},
+  		keyframes: {
+  			'accordion-down': {
+  				from: {
+  					height: '0'
+  				},
+  				to: {
+  					height: 'var(--radix-accordion-content-height)'
+  				}
+  			},
+  			'accordion-up': {
+  				from: {
+  					height: 'var(--radix-accordion-content-height)'
+  				},
+  				to: {
+  					height: '0'
+  				}
+  			}
+  		},
+  		animation: {
+  			'accordion-down': 'accordion-down 0.2s ease-out',
+  			'accordion-up': 'accordion-up 0.2s ease-out'
+  		}
+  	}
   },
   plugins: [],
 };