fix(auth): role-aware post-login landing to avoid 403 for non-MeasurementTec

Login always redirected to measure.select_recipe, which is gated by
@role_required("MeasurementTec"). A Maker-only (or Metrologist-only) user
was therefore bounced straight to a 403 right after a successful login.

Add _post_login_landing() which selects the landing endpoint from the user's
roles (MeasurementTec -> measure, Maker -> maker recipes, Metrologist ->
statistics, admin -> users, else profile). Used for both fresh login and the
already-authenticated short-circuit.

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

src/frontend/flask_app/blueprints/auth.py

@@ -39,15 +39,32 @@ def role_required(*roles):
     return decorator
 
 
+def _post_login_landing():
+    """Pick the landing endpoint based on the logged-in user's roles.
+
+    A Maker-only user must not be bounced to /measure (MeasurementTec-only),
+    which would raise a 403 right after login. Order of preference follows the
+    primary operator flow first, then editing, analysis, admin.
+    """
+    user = session.get("user", {})
+    roles = user.get("roles", [])
+    if "MeasurementTec" in roles:
+        return url_for("measure.select_recipe")
+    if "Maker" in roles:
+        return url_for("maker.recipe_list")
+    if "Metrologist" in roles:
+        return url_for("statistics.dashboard")
+    if user.get("is_admin"):
+        return url_for("admin.user_list")
+    return url_for("auth.profile")
+
+
 @auth_bp.route("/login", methods=["GET", "POST"])
 def login():
     """Login page and form handler."""
-    # Se già loggato, redirect a home
+    # Se già loggato, redirect alla home in base al ruolo
     if session.get("api_key"):
-        try:
-            return redirect(url_for("measure.select_recipe"))
-        except Exception:
-            return redirect(url_for("auth.profile"))
+        return redirect(_post_login_landing())
 
     if request.method == "POST":
         username = request.form.get("username", "").strip()
@@ -91,11 +108,8 @@ def login():
 
             flash(_("Benvenuto, %(name)s!", name=user.get("display_name", username)), "success")
 
-            # Redirect dopo login
-            try:
-                return redirect(url_for("measure.select_recipe"))
-            except Exception:
-                return redirect(url_for("auth.profile"))
+            # Redirect dopo login (in base al ruolo)
+            return redirect(_post_login_landing())
 
         except Exception as e:
             flash(_("Errore di connessione al server: %(error)s", error=str(e)), "error")