SEO: Improve meta titles, descriptions & internal links for top 10 pages

- Rewrite meta titles to be more compelling with power words and 2026 dates
- Shorten meta descriptions to ~150 chars with clear CTAs
- Remove double-branding from title tags (was: title | UK Data Services | UK Data Services Blog)
- Update internal cross-links between related scraping/analytics articles
- Focus: top 10 pages by impressions from Google Search Console

oauth-callback.php

@@ -1,13 +0,0 @@
-<?php
-if (isset($_GET['code'])) {
-    echo '<h2>QBO OAuth Success</h2>';
-    echo '<p><strong>Authorization Code:</strong></p>';
-    echo '<pre>' . htmlspecialchars($_GET['code']) . '</pre>';
-    echo '<p><strong>Realm ID:</strong></p>';
-    echo '<pre>' . htmlspecialchars($_GET['realmId'] ?? 'N/A') . '</pre>';
-    echo '<p>Copy the code above and give it to Emma.</p>';
-} else {
-    echo '<h2>Error</h2>';
-    echo '<pre>' . htmlspecialchars($_GET['error'] ?? 'Unknown error') . '</pre>';
-}
-?>