feat(roles): add dedicated Supervisor (capoturno) role

Until now the out-of-tolerance authorization ("Autorizzazione capoturno")
required is_admin, conflating shift-leader authority with full system
administration. Introduce a combinable Supervisor role so a capoturno can
authorize overrides without admin privileges (roadmap D-0.8 / Phase 2).

Backend:
- users router: add "Supervisor" to the allowed roles (centralized as
  VALID_ROLES, deduplicating the create/update validation).
- middleware: add require_supervisor dependency (admins still bypass).

Frontend:
- measure.validate_supervisor: authorize users with the Supervisor role OR
  is_admin (was is_admin only).
- admin/users: Supervisor checkbox + orange role badge.
- profile: explicit Supervisor badge styling.
- EN translation for the new role label.

roles is a free JSON column, so no migration is required.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/frontend/flask_app/blueprints/measure.py

@@ -347,7 +347,8 @@ def validate_supervisor():
         return jsonify({"error": True, "detail": "Credenziali non valide"}), 401
 
     user = resp.get("user", {})
-    if not user.get("is_admin"):
+    is_supervisor = "Supervisor" in (user.get("roles") or [])
+    if not (is_supervisor or user.get("is_admin")):
         return jsonify({"error": True, "detail": "Utente non autorizzato (richiesto capoturno)"}), 403
 
     return jsonify({"authorized": True, "supervisor": user.get("display_name", username)}), 200

src/frontend/flask_app/templates/admin/users.html

@@ -78,7 +78,8 @@
                           :class="{
                             'bg-blue-100 dark:bg-blue-900/30 text-blue-700 dark:text-blue-300': role === 'Maker',
                             'bg-green-100 dark:bg-green-900/30 text-green-700 dark:text-green-300': role === 'MeasurementTec',
-                            'bg-purple-100 dark:bg-purple-900/30 text-purple-700 dark:text-purple-300': role === 'Metrologist'
+                            'bg-purple-100 dark:bg-purple-900/30 text-purple-700 dark:text-purple-300': role === 'Metrologist',
+                            'bg-orange-100 dark:bg-orange-900/30 text-orange-700 dark:text-orange-300': role === 'Supervisor'
                           }"
                           x-text="role"></span>
                   </template>
@@ -233,6 +234,11 @@
                      class="rounded border-[var(--border-color)] text-primary focus:ring-primary/30">
               <span class="text-sm text-[var(--text-primary)]">Metrologist</span>
             </label>
+            <label class="flex items-center gap-2 cursor-pointer">
+              <input type="checkbox" x-model="form.roles" value="Supervisor"
+                     class="rounded border-[var(--border-color)] text-primary focus:ring-primary/30">
+              <span class="text-sm text-[var(--text-primary)]">{{ _('Supervisor (capoturno)') }}</span>
+            </label>
           </div>
         </div>
 

src/frontend/flask_app/templates/auth/profile.html

@@ -87,6 +87,8 @@
                         bg-blue-100 dark:bg-blue-900/30 text-blue-800 dark:text-blue-200 border border-blue-200 dark:border-blue-800
                       {% elif role == 'Metrologist' %}
                         bg-purple-100 dark:bg-purple-900/30 text-purple-800 dark:text-purple-200 border border-purple-200 dark:border-purple-800
+                      {% elif role == 'Supervisor' %}
+                        bg-orange-100 dark:bg-orange-900/30 text-orange-800 dark:text-orange-200 border border-orange-200 dark:border-orange-800
                       {% else %}
                         bg-slate-100 dark:bg-slate-700 text-slate-800 dark:text-slate-200 border border-slate-200 dark:border-slate-600
                       {% endif %}">

src/frontend/flask_app/translations/en/LC_MESSAGES/messages.po

@@ -2185,3 +2185,6 @@ msgstr "E.g. LOT-2026-001 (optional)"
 msgid "Es. SN-000123 (opzionale)"
 msgstr "E.g. SN-000123 (optional)"
 
+msgid "Supervisor (capoturno)"
+msgstr "Supervisor (shift leader)"
+