fix(api,frontend): delete is the true inverse of adopt, no reseed

/creatures/:id/delete now just removes the row, matching how
POST /creatures (adopt) just inserts one — no side effects on anything
else. The auto-reseed was scope creep for a feature that only ever made
sense as a public marketing-site action; now that delete lives in the app
itself as a per-creature control, that safety net isn't needed.

Adds a Delete button next to Feed/Play/Sleep/Revive on every creature
card, same creatureAction() plumbing as the existing actions.

frontend/app.js

@@ -29,6 +29,8 @@ const i18n = {
     play: '🎮 Play',
     sleep: '💤 Sleep',
     revive: '✨ Revive',
+    delete: '🗑️',
+    delete_title: 'Delete permanently — the opposite of Adopt',
     alive: 'Alive',
     dead: 'Dead',
     empty_title: 'No creatures yet!',
@@ -47,6 +49,8 @@ const i18n = {
     play: '🎮 Jouer',
     sleep: '💤 Dormir',
     revive: '✨ Ressusciter',
+    delete: '🗑️',
+    delete_title: "Supprimer definitivement — l'oppose d'Adopter",
     alive: 'Vivant',
     dead: 'Mort',
     empty_title: 'Pas encore de créatures !',
@@ -226,6 +230,7 @@ function renderCreatures() {
           ` : `
             <button class="action-btn revive" onclick="creatureAction('${c.id}', 'revive')">${t('revive')}</button>
           `}
+          <button class="action-btn delete" title="${t('delete_title')}" onclick="creatureAction('${c.id}', 'delete')">${t('delete')}</button>
         </div>
       </div>
     `;

frontend/style.css

@@ -295,6 +295,14 @@ body::before {
   color: var(--accent-green);
 }
 
+.action-btn.delete {
+  background: rgba(255, 68, 102, 0.1);
+  border-color: rgba(255, 68, 102, 0.2);
+  color: var(--accent-red);
+  flex: 0 0 auto;
+  width: 44px;
+}
+
 /* ---- FAB ---- */
 .fab {
   position: fixed;