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/backend/api/middleware/__init__.py

@@ -6,6 +6,7 @@ from src.backend.api.middleware.api_key import (
     require_maker,
     require_measurement_tec,
     require_metrologist,
+    require_supervisor,
     require_admin_user,
 )
 from src.backend.api.middleware.logging import AccessLogMiddleware
@@ -19,6 +20,7 @@ __all__ = [
     "require_maker",
     "require_measurement_tec",
     "require_metrologist",
+    "require_supervisor",
     "require_admin_user",
     "AccessLogMiddleware",
     "RateLimitMiddleware",

src/backend/api/middleware/api_key.py

@@ -68,4 +68,5 @@ def require_admin():
 require_maker = require_role("Maker")
 require_measurement_tec = require_role("MeasurementTec")
 require_metrologist = require_role("Metrologist")
+require_supervisor = require_role("Supervisor")
 require_admin_user = require_admin()

src/backend/api/routers/users.py

@@ -11,6 +11,10 @@ from src.backend.services.auth_service import create_user, hash_password, regene
 
 router = APIRouter(prefix="/api/users", tags=["users"])
 
+# Combinable user roles. Supervisor (capoturno) authorizes out-of-tolerance
+# overrides during measurement without needing full admin privileges.
+VALID_ROLES = {"Maker", "MeasurementTec", "Metrologist", "Supervisor"}
+
 
 @router.get("", response_model=list[UserResponse])
 async def list_users(
@@ -40,12 +44,11 @@ async def create_new_user(
             detail=f"Username '{data.username}' already exists",
         )
     # Validate roles
-    valid_roles = {"Maker", "MeasurementTec", "Metrologist"}
     for role in data.roles:
-        if role not in valid_roles:
+        if role not in VALID_ROLES:
             raise HTTPException(
                 status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
-                detail=f"Invalid role '{role}'. Valid roles: {valid_roles}",
+                detail=f"Invalid role '{role}'. Valid roles: {VALID_ROLES}",
             )
     user = await create_user(
         db,
@@ -77,12 +80,11 @@ async def update_user(
     update_data = data.model_dump(exclude_unset=True)
     # Validate roles if provided
     if "roles" in update_data:
-        valid_roles = {"Maker", "MeasurementTec", "Metrologist"}
         for role in update_data["roles"]:
-            if role not in valid_roles:
+            if role not in VALID_ROLES:
                 raise HTTPException(
                     status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
-                    detail=f"Invalid role '{role}'. Valid roles: {valid_roles}",
+                    detail=f"Invalid role '{role}'. Valid roles: {VALID_ROLES}",
                 )
     for field, value in update_data.items():
         setattr(user, field, value)