feat: add editable 301 redirects via dedicated panel page

- New "Redirections" page in panel (blueprint + content) with a structure
  field: old URL (text) → target page (pages field, auto-resolves URL)
- error.php controller intercepts 404s, checks redirect map, fires go() 301
- Cache (file driver) invalidated on redirections page update or slug change
- Removed catch-all route that was breaking Kirby multilingual routing

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

site/config/config.php

@@ -12,8 +12,23 @@ return [
 
     'thumbs' => require __DIR__ . '/thumbs.php',
 
+    'cache' => [
+        'redirects' => ['type' => 'file'],
+    ],
+
+    'hooks' => [
+        'page.update:after' => function ($newPage) {
+            if ($newPage->id() === 'redirections') {
+                kirby()->cache('redirects')->remove('map');
+            }
+        },
+        'page.changeSlug:after' => function () {
+            kirby()->cache('redirects')->remove('map');
+        },
+    ],
+
     'routes' => [
-        require(__DIR__ . '/routes/download-white-paper.php')
+        require(__DIR__ . '/routes/download-white-paper.php'),
     ],
 
     'tobimori.seo' => [