feat: clickable character cards, default character, rename Archivio → Libreria

- CharacterList: entire card is clickable to enter edit mode
- CharacterList: uses ConfirmModal for delete (replaces browser confirm)
- CharacterList: action buttons stop propagation to avoid double-nav
- ContentPage: auto-selects first active character as default
- Rename "Archivio Contenuti" → "Libreria Contenuti" everywhere
- Mobile-safe grid for character cards

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/ContentArchive.jsx

@@ -87,12 +87,12 @@ export default function ContentArchive() {
     <div style={{ animation: 'fade-up 0.5s ease-out both' }}>
       <div style={{ marginBottom: '2rem', display: 'flex', alignItems: 'center', justifyContent: 'space-between' }}>
         <div>
-          <span className="editorial-tag">Archivio</span>
+          <span className="editorial-tag">Libreria</span>
           <div className="editorial-line" />
           <h2 style={{ fontFamily: "'Fraunces', serif", fontSize: '1.75rem', fontWeight: 600, letterSpacing: '-0.02em', color: 'var(--ink)', margin: '0.5rem 0 0.3rem' }}>
-            Archivio Contenuti
+            Libreria Contenuti
           </h2>
-          <p style={{ fontSize: '0.875rem', color: 'var(--ink-muted)', margin: 0 }}>Tutti i contenuti generati</p>
+          <p style={{ fontSize: '0.875rem', color: 'var(--ink-muted)', margin: 0 }}>I tuoi contenuti generati</p>
         </div>
         <Link to="/content" style={{ fontSize: '0.8rem', color: 'var(--accent)', textDecoration: 'none', fontWeight: 600 }}>
           ← Genera nuovo