feat(inventory): remove the requiredLevel equip gate from the detail panel

The API can no longer emit ITEM_LEVEL_REQUIREMENT_NOT_MET (Task 8 removed
the level gate server-side) and InventoryItem.item no longer carries
requiredLevel (Task 12). Drop the characterLevel input, the
meetsLevelRequirement computed, the associated template branch and copy,
and the dead German error-message mapping. Update fixtures across the
inventory specs to the real InventoryItem/CharacterResponse shapes.

apps/web/src/app/features/inventory/inventory-detail-panel.component.html

@@ -6,7 +6,7 @@
         <h2 class="inventory-detail__name" data-detail-name>{{ item.item.name }}</h2>
         <p class="inventory-detail__rarity" data-detail-rarity>{{ rarityLabel() }}</p>
         @if (slotLabel(); as slot) {
-          <p class="inventory-detail__meta">{{ slot }} · Stufe {{ item.item.requiredLevel }}</p>
+          <p class="inventory-detail__meta">{{ slot }}</p>
         }
       </div>
     </div>
@@ -38,10 +38,6 @@
         <span class="inventory-detail__equipped" data-detail-equipped>Ausgerüstet</span>
       } @else if (!isEquippable()) {
         <span class="inventory-detail__note">Nicht ausrüstbar</span>
-      } @else if (!meetsLevelRequirement()) {
-        <button type="button" class="inventory-detail__equip" data-detail-equip disabled>
-          Benötigt Stufe {{ item.item.requiredLevel }}
-        </button>
       } @else {
         <button
           type="button"