Swap to shadcn components and polish the design

Components (added via the shadcn MCP/CLI):
- Navbar: NavigationMenu on desktop, Sheet on mobile; drops
  Navbar.module.css and the hand-rolled slide-down menu
- Buttons: shadcn Button via a shared ContactButtons component
  (replaces Button.js and its CSS module)
- Card for price cards, testimonials, the business block and plan;
  Table for prices; Input/Textarea/Label/NativeSelect/RadioGroup and
  Alert in the quote form; Separator in the footer
- Components import cn from @/lib/utils (not the new "cn" package);
  accordion moved to the unified radix-ui package

Design tweaks:
- Geist Sans is actually applied (font variables were on <body>, but
  Tailwind reads them on <html>, so the site fell back to system fonts)
- Theme primary set to the existing brand blue; slightly smaller radius
- Balanced, tighter heading tracking; muted secondary text
- 44px contact buttons; 16px FAQ text; tighter homepage spacing
- Full-width selects with 16px text on phones (no iOS zoom)

Co-Authored-By: Claude Opus 5.5 <[email protected]>

package.json

@@ -9,11 +9,11 @@
     "lint": "eslint ."
   },
   "dependencies": {
-    "@radix-ui/react-accordion": "^1.2.20",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
     "lucide-react": "^1.49.0",
     "next": "^16.3.7",
+    "radix-ui": "^1.6.7",
     "react": "^19.3.0",
     "react-dom": "^19.3.0",
     "sharp": "^0.35.5",