feat(client): add admin GUI for stations CRUD and recipe assignments

Adds a complete browser-based interface for managing stations,
closing the last deliverable of rev04 Phase 1.

- New /admin/stations page with stations table, create/edit modal,
  delete confirmation and dedicated recipe-assignment modal
- Proxy endpoints under /admin/api/stations/* covering CRUD and
  recipe assign/unassign so all admin operations stay behind the
  Flask CSRF + admin_required guard
- Navbar entry "Stazioni" (desktop + mobile), visible to admins only
- 10 new tests covering page render, every proxy and the non-admin
  redirect

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

client/templates/components/navbar.html

@@ -79,7 +79,7 @@
            class="nav-link group flex items-center gap-2 px-3 py-2 rounded-lg text-sm font-medium
                   text-[var(--text-secondary)] hover:text-primary hover:bg-primary-50 dark:hover:bg-primary-900/20
                   transition-colors duration-200
-                  {% if request.endpoint and request.endpoint.startswith('admin.') %}
+                  {% if request.endpoint == 'admin.user_list' %}
                     text-primary bg-primary-50 dark:bg-primary-900/20
                   {% endif %}">
           <!-- Users Icon -->
@@ -88,6 +88,20 @@
           </svg>
           <span>{{ _('Utenti') }}</span>
         </a>
+
+        <a href="{{ url_for('admin.station_list') }}"
+           class="nav-link group flex items-center gap-2 px-3 py-2 rounded-lg text-sm font-medium
+                  text-[var(--text-secondary)] hover:text-primary hover:bg-primary-50 dark:hover:bg-primary-900/20
+                  transition-colors duration-200
+                  {% if request.endpoint == 'admin.station_list' %}
+                    text-primary bg-primary-50 dark:bg-primary-900/20
+                  {% endif %}">
+          <!-- Station / Workstation Icon -->
+          <svg class="w-4.5 h-4.5" fill="none" stroke="currentColor" stroke-width="1.75" viewBox="0 0 24 24">
+            <path stroke-linecap="round" stroke-linejoin="round" d="M9 17.25v1.007a3 3 0 01-.879 2.122L7.5 21h9l-.621-.621A3 3 0 0115 18.257V17.25m6-12V15a2.25 2.25 0 01-2.25 2.25H5.25A2.25 2.25 0 013 15V5.25m18 0A2.25 2.25 0 0018.75 3H5.25A2.25 2.25 0 003 5.25m18 0V12a2.25 2.25 0 01-2.25 2.25H5.25A2.25 2.25 0 013 12V5.25"/>
+          </svg>
+          <span>{{ _('Stazioni') }}</span>
+        </a>
         {% endif %}
 
       </div>
@@ -264,7 +278,7 @@
       </a>
       {% endif %}
 
-      {# Admin: Utenti #}
+      {# Admin: Utenti + Stazioni #}
       {% if current_user.get('is_admin') %}
       <a href="{{ url_for('admin.user_list') }}"
          class="flex items-center gap-3 px-3 py-2.5 rounded-lg text-sm font-medium
@@ -275,6 +289,16 @@
         </svg>
         {{ _('Utenti') }}
       </a>
+
+      <a href="{{ url_for('admin.station_list') }}"
+         class="flex items-center gap-3 px-3 py-2.5 rounded-lg text-sm font-medium
+                text-[var(--text-secondary)] hover:text-primary hover:bg-primary-50 dark:hover:bg-primary-900/20
+                transition-colors">
+        <svg class="w-5 h-5" fill="none" stroke="currentColor" stroke-width="1.75" viewBox="0 0 24 24">
+          <path stroke-linecap="round" stroke-linejoin="round" d="M9 17.25v1.007a3 3 0 01-.879 2.122L7.5 21h9l-.621-.621A3 3 0 0115 18.257V17.25m6-12V15a2.25 2.25 0 01-2.25 2.25H5.25A2.25 2.25 0 013 15V5.25m18 0A2.25 2.25 0 0018.75 3H5.25A2.25 2.25 0 003 5.25m18 0V12a2.25 2.25 0 01-2.25 2.25H5.25A2.25 2.25 0 013 12V5.25"/>
+        </svg>
+        {{ _('Stazioni') }}
+      </a>
       {% endif %}
 
     </div>