fix: improve SEO with pre-rendering and dynamic meta tags

Critical SEO improvements to fix Google Search Console indexing:

## Sitemap Updates:
- Added missing Invoice Editor and What's New pages
- Updated all lastmod dates to 2025-10-15
- Increased editor tools priority to 0.9
- Added organizational comments
- Fixed /whats-new route (was /release-notes)

## Pre-rendering Implementation:
- Added react-snap for static HTML generation
- Configured to pre-render all tool pages
- Solves React SPA indexing issue
- Crawlers now see full HTML content

## Dynamic Meta Tags:
- Added react-helmet-async for SEO management
- Created reusable SEO component with:
  - Dynamic titles and descriptions
  - Open Graph tags (Facebook)
  - Twitter Card tags
  - JSON-LD structured data
  - Canonical URLs
- Wrapped App with HelmetProvider
- Added SEO to Home page

## Route Fixes:
- Added /whats-new route (primary)
- Kept /release-notes as fallback
- Consistent routing across app

## Documentation:
- Created comprehensive SEO_FIX_GUIDE.md
- Step-by-step Google Search Console instructions
- Troubleshooting guide
- Timeline expectations
- Testing procedures

These changes will dramatically improve Google indexing and search visibility.

src/components/SEO.js

@@ -0,0 +1,75 @@
+import React from 'react';
+import { Helmet } from 'react-helmet-async';
+
+const SEO = ({ 
+  title, 
+  description, 
+  keywords,
+  path = '/',
+  type = 'website',
+  image = 'https://dewe.dev/og-image.png'
+}) => {
+  const siteUrl = 'https://dewe.dev';
+  const fullUrl = `${siteUrl}${path}`;
+  const fullTitle = title ? `${title} | Developer Tools` : 'Developer Tools - Essential Web Developer Utilities';
+  const defaultDescription = 'Free online developer tools for JSON, CSV, Base64, URL encoding, code beautification, and more. Privacy-first, no data storage, all processing in your browser.';
+  const metaDescription = description || defaultDescription;
+  const defaultKeywords = 'developer tools, json editor, csv converter, base64 encoder, url encoder, code beautifier, diff tool, web developer utilities, online tools';
+  const metaKeywords = keywords || defaultKeywords;
+
+  return (
+    <Helmet>
+      {/* Basic Meta Tags */}
+      <title>{fullTitle}</title>
+      <meta name="description" content={metaDescription} />
+      <meta name="keywords" content={metaKeywords} />
+      <link rel="canonical" href={fullUrl} />
+
+      {/* Open Graph / Facebook */}
+      <meta property="og:type" content={type} />
+      <meta property="og:url" content={fullUrl} />
+      <meta property="og:title" content={fullTitle} />
+      <meta property="og:description" content={metaDescription} />
+      <meta property="og:image" content={image} />
+      <meta property="og:site_name" content="Developer Tools" />
+
+      {/* Twitter Card */}
+      <meta name="twitter:card" content="summary_large_image" />
+      <meta name="twitter:url" content={fullUrl} />
+      <meta name="twitter:title" content={fullTitle} />
+      <meta name="twitter:description" content={metaDescription} />
+      <meta name="twitter:image" content={image} />
+
+      {/* Additional SEO Tags */}
+      <meta name="robots" content="index, follow" />
+      <meta name="googlebot" content="index, follow" />
+      <meta name="author" content="Developer Tools" />
+      <meta name="language" content="English" />
+      
+      {/* JSON-LD Structured Data */}
+      <script type="application/ld+json">
+        {JSON.stringify({
+          "@context": "https://schema.org",
+          "@type": "WebApplication",
+          "name": fullTitle,
+          "description": metaDescription,
+          "url": fullUrl,
+          "applicationCategory": "DeveloperApplication",
+          "operatingSystem": "Any",
+          "offers": {
+            "@type": "Offer",
+            "price": "0",
+            "priceCurrency": "USD"
+          },
+          "provider": {
+            "@type": "Organization",
+            "name": "Developer Tools",
+            "url": siteUrl
+          }
+        })}
+      </script>
+    </Helmet>
+  );
+};
+
+export default SEO;