Add social preview image and iPhone/Android EXIF guides

New 1200x630 preview card with the new logo, two high-intent guides,
cross-linked related lists, updated sitemap, footer and guides index.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

guides/what-is-c2pa/index.html

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 <div class="cta"><p><strong>See what your own photo is hiding.</strong> Untrace lists every metadata block, then removes it, all inside your browser.</p><a class="btn btn-primary" href="/#tool">Scan a photo</a></div>
           <h2>Common questions</h2>
           <h3>Is C2PA the same as EXIF?</h3><p>No. EXIF records camera and location details. C2PA records a signed history of creation and edits. Untrace reads and removes both.</p><h3>Can C2PA be forged?</h3><p>The signature protects the manifest from tampering, but anyone can create a manifest with their own certificate, so trust depends on who signed it.</p>
-          <nav class="related" aria-label="Related guides"><h2>Keep reading</h2><ul><li><a href="/guides/remove-gps-from-photo/">How to remove GPS location from a photo</a></li><li><a href="/guides/what-is-exif-data/">What is EXIF data?</a></li></ul></nav>
+          <nav class="related" aria-label="Related guides"><h2>Keep reading</h2><ul><li><a href="/guides/remove-gps-from-photo/">How to remove GPS location from a photo</a></li><li><a href="/guides/remove-exif-data-iphone/">How to remove EXIF data from photos on iPhone</a></li><li><a href="/guides/remove-exif-data-android/">How to remove EXIF and location data from photos on Android</a></li><li><a href="/guides/what-is-exif-data/">What is EXIF data?</a></li></ul></nav>
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