feat(frontend): add archive format family, compression control, and fixed double-extension parsing

Also adds a --color-family-archives CSS variable (light + dark) that
the plan didn't call out explicitly but is needed for the new family
tile/icon to render with a color instead of falling back silently.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/data/formats.js

@@ -15,4 +15,8 @@ export const FORMAT_FAMILIES = [
     key: 'ebooks',
     formats: ['epub', 'fb2', 'lrf', 'mobi', 'pdb', 'rb', 'snb', 'tcr', 'azw3', 'pdf'],
   },
+  {
+    key: 'archives',
+    formats: ['zip', 'tar', 'tar.gz', 'tar.bz2', '7z', 'tar.7z', 'rar'],
+  },
 ];