feat: add Stirling PDF toolkit

Added Stirling PDF as the 4th tool in the kit:

📄 Stirling PDF Features:
- 50+ PDF operations (merge, split, convert)
- OCR processing for scanned documents
- Digital signatures and watermarks
- Privacy-first: locally hosted, no cloud dependency
- Open source with 69.6k+ GitHub stars

🎨 Visual:
- Purple-blue gradient matching brand
- PDF document icon with lines
- Badges: Privacy, Open Source, Free

📊 Updates:
- Stats section: 3 → 4 Tools
- Footer: Added Stirling link
- README: Added tool description
- Grid layout: Now displays 4 tools responsively

🔗 URL: https://stirling.kit.pivoine.art

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

README.md

@@ -134,6 +134,7 @@ Tailwind CSS 4 uses a new CSS-first configuration approach:
 - **Vert** - Privacy-focused file converter (images, audio, documents)
 - **Paint** - Browser-based image editor
 - **Pastel** - Modern color manipulation toolkit with palette generation and accessibility testing
+- **Stirling** - Powerful PDF toolkit with 50+ operations (merge, split, convert, OCR, sign)
 
 ## CI/CD Pipeline
 

components/Footer.tsx

@@ -24,7 +24,7 @@ export default function Footer() {
               Your Creative Toolkit
             </p>
             <div className="mt-4 inline-flex items-center gap-2 px-3 py-1 rounded-full bg-purple-500/10 border border-purple-500/20">
-              <span className="text-xs font-medium text-purple-400">3 Tools</span>
+              <span className="text-xs font-medium text-purple-400">4 Tools</span>
               <span className="text-gray-600">•</span>
               <span className="text-xs text-gray-500">Open Source</span>
             </div>
@@ -63,6 +63,7 @@ export default function Footer() {
               <a href="https://vert.kit.pivoine.art" className="text-gray-400 hover:text-green-400 transition-colors text-sm">Vert</a>
               <a href="https://paint.kit.pivoine.art" className="text-gray-400 hover:text-orange-400 transition-colors text-sm">Paint</a>
               <a href="https://pastel.kit.pivoine.art" className="text-gray-400 hover:text-purple-400 transition-colors text-sm">Pastel</a>
+              <a href="https://stirling.kit.pivoine.art" className="text-gray-400 hover:text-blue-400 transition-colors text-sm">Stirling</a>
             </div>
           </div>
         </motion.div>

components/Stats.tsx

@@ -4,7 +4,7 @@ import { motion } from 'framer-motion';
 
 const stats = [
   {
-    number: '3',
+    number: '4',
     label: 'Tools',
     icon: (
       <svg className="w-6 h-6" fill="none" stroke="currentColor" viewBox="0 0 24 24">

components/ToolsGrid.tsx

@@ -43,6 +43,19 @@ const tools = [
       </svg>
     ),
   },
+  {
+    title: 'Stirling',
+    description: 'Powerful locally-hosted PDF toolkit with 50+ operations. Merge, split, convert, OCR, sign, and manipulate PDFs with complete privacy.',
+    url: 'https://stirling.kit.pivoine.art',
+    gradient: 'gradient-purple-blue',
+    badges: ['Privacy', 'Open Source', 'Free'],
+    icon: (
+      <svg className="w-12 h-12 text-white" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+        <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M7 21h10a2 2 0 002-2V9.414a1 1 0 00-.293-.707l-5.414-5.414A1 1 0 0012.586 3H7a2 2 0 00-2 2v14a2 2 0 002 2z" />
+        <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M10 12h4m-4 4h4" />
+      </svg>
+    ),
+  },
 ];
 
 export default function ToolsGrid() {