feat: Refactor example page and showcase components

- Updated ExamplePage to use a single Showcase component instead of separate InputShowCase and FormShowcase components.
- Added CheckboxShowcase, FormShowcase, and InputShowCase components to the showcase directory.
- Implemented Checkbox component with various states and styles.
- Enhanced InputShowCase to demonstrate different input types and states.
- Integrated new styles for checkbox variants and states.
- Updated package dependencies to include @rc-component/checkbox.

packages/ui/src/globals.css

@@ -62,26 +62,57 @@
   --color-gray-800: #1f2937;
   --color-gray-900: #111827;
 
-  /* Semantics */
+  /* -------------------------------
+     COLORS: SEMANTICS (COMPLETED)
+     ------------------------------- */
+
+  /* Error (Red) */
   --color-error-50: #fef2f2;
   --color-error-100: #fee2e2;
+  --color-error-200: #fecaca;
+  --color-error-300: #fca5a5;
+  --color-error-400: #f87171;
   --color-error-500: #ef4444;
   --color-error-600: #dc2626;
+  --color-error-700: #b91c1c;
+  --color-error-800: #991b1b;
+  --color-error-900: #7f1d1d;
 
+  /* Warning (Amber/Orange) */
   --color-warning-50: #fffbeb;
   --color-warning-100: #fef3c7;
+  --color-warning-200: #fde68a;
+  --color-warning-300: #fcd34d;
+  --color-warning-400: #fbbf24;
   --color-warning-500: #f59e0b;
   --color-warning-600: #d97706;
+  --color-warning-700: #b45309;
+  --color-warning-800: #92400e;
+  --color-warning-900: #78350f;
 
+  /* Success (Green) */
   --color-success-50: #f0fdf4;
   --color-success-100: #dcfce7;
+  --color-success-200: #bbf7d0;
+  --color-success-300: #86efac;
+  --color-success-400: #4ade80;
   --color-success-500: #22c55e;
   --color-success-600: #16a34a;
+  --color-success-700: #15803d;
+  --color-success-800: #166534;
+  --color-success-900: #14532d;
 
+  /* Info (Blue/Sky) */
   --color-info-50: #f0f9ff;
   --color-info-100: #e0f2fe;
+  --color-info-200: #bae6fd;
+  --color-info-300: #7dd3fc;
+  --color-info-400: #38bdf8;
   --color-info-500: #0ea5e9;
   --color-info-600: #0284c7;
+  --color-info-700: #0369a1;
+  --color-info-800: #075985;
+  --color-info-900: #0c4a6e;
 
   /* -------------------------------
      FORM ITEM SPECIFICS