workout generator audit: rules engine, structure rules, split patterns, injury UX, metadata cleanup

- Add rules_engine.py with quantitative rules for all 8 workout types
- Add quality gate retry loop in generate_single_workout()
- Expand calibrate_structure_rules to all 120 combinations (8 types × 5 goals × 3 sections)
- Wire WeeklySplitPattern DB records into _pick_weekly_split()
- Enforce movement patterns from WorkoutStructureRule in exercise selection
- Add straight-set strength support (single main lift, 4-6 rounds)
- Add modality consistency check for duration-dominant workout types
- Add InjuryStep component to onboarding and preferences
- Add sibling exercise exclusion in regenerate and preview_day endpoints
- Display generator warnings on dashboard
- Expand fix_rep_durations, fix_exercise_flags, fix_movement_pattern_typo
- Add audit_exercise_data and check_rules_drift management commands
- Add Next.js frontend with dashboard, onboarding, preferences, history pages
- Add generator app with ML-powered workout generation pipeline
- 96 new tests across 7 test modules

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

registered_user/views.py

@@ -48,10 +48,18 @@ def create_registered_user(request):
 
 @api_view(['POST'])
 def login_registered_user(request):
-    email = request.data["email"]
-    password = request.data["password"]
-    
+    email = request.data.get("email", "").strip()
+    password = request.data.get("password", "")
+
+    # Try authenticating with the input as username first, then by email lookup
     user = authenticate(username=email, password=password)
+    if user is None:
+        from django.contrib.auth.models import User
+        try:
+            user_obj = User.objects.get(email=email)
+            user = authenticate(username=user_obj.username, password=password)
+        except User.DoesNotExist:
+            pass
 
     if user is not None:
         registered_user = get_object_or_404(RegisteredUser, user=user)
@@ -61,7 +69,7 @@ def login_registered_user(request):
         data["token"] = token
         return Response(data,status=status.HTTP_200_OK)
     else:
-        return Response({}, status=status.HTTP_404_NOT_FOUND)
+        return Response({"detail": "Invalid email or password"}, status=status.HTTP_404_NOT_FOUND)
 
 
 @api_view(['POST'])