feat(accounts): home district with 6-month cooldown

- accounts/models.py: add district_changed_at DateTimeField + VALID_DISTRICTS constant (14 Kerala districts)
- migration 0013_user_district_changed_at: nullable DateTimeField, no backfill
- WebRegisterForm: accept optional district during signup, stamp district_changed_at
- UpdateProfileView: enforce 183-day cooldown with human-readable error
- LoginView/WebRegisterView/StatusView: include district_changed_at in responses

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

mobile_api/forms/user_forms.py

@@ -45,7 +45,7 @@ class WebRegisterForm(forms.ModelForm):
 
     class Meta:
         model = User
-        fields = ['first_name', 'last_name', 'email', 'phone_number', 'password', 'confirm_password']
+        fields = ['first_name', 'last_name', 'email', 'phone_number', 'password', 'confirm_password', 'district']
 
     def clean_email(self):
         email = self.cleaned_data.get('email')
@@ -76,6 +76,12 @@ class WebRegisterForm(forms.ModelForm):
         # Mark as a customer / end-user
         user.is_customer = True
         user.role = 'customer'
+        from django.utils import timezone
+        from accounts.models import VALID_DISTRICTS
+        if user.district and user.district in VALID_DISTRICTS:
+            user.district_changed_at = timezone.now()
+        elif user.district:
+            user.district = None  # reject invalid district silently
         if commit:
             user.save()
         return user

mobile_api/views/user.py

@@ -58,6 +58,11 @@ class WebRegisterView(View):
                     'username': user.username,
                     'email': user.email,
                     'phone_number': user.phone_number,
+                    'district': user.district or '',
+                    'district_changed_at': user.district_changed_at.isoformat() if user.district_changed_at else None,
+                    'first_name': user.first_name,
+                    'last_name': user.last_name,
+                    'eventify_id': user.eventify_id or '',
                 }
                 return JsonResponse(response, status=201)
             log("warning", "Web registration failed", request=request, logger_data=dict(errors=form.errors))
@@ -93,6 +98,7 @@ class LoginView(View):
                     'role': user.role,
                     'pincode': user.pincode,
                     'district': user.district,
+                    'district_changed_at': user.district_changed_at.isoformat() if user.district_changed_at else None,
                     'state': user.state,
                     'country': user.country,
                     'place': user.place,
@@ -124,6 +130,8 @@ class StatusView(View):
                 "username": user.username,
                 "email": user.email,
                 "eventify_id": user.eventify_id or '',
+                "district": user.district or '',
+                "district_changed_at": user.district_changed_at.isoformat() if user.district_changed_at else None,
             })
 
         except Exception as e:
@@ -245,15 +253,33 @@ class UpdateProfileView(View):
                     user.pincode = None
                     updated_fields.append('pincode')
 
-            # Update district
+            # Update district (with 6-month cooldown)
             if 'district' in json_data:
-                district = json_data.get('district', '').strip()
-                if district:
-                    user.district = district
-                    updated_fields.append('district')
-                elif district == '':
-                    user.district = None
-                    updated_fields.append('district')
+                from django.utils import timezone
+                from datetime import timedelta
+                from accounts.models import VALID_DISTRICTS
+
+                COOLDOWN = timedelta(days=183)  # ~6 months
+                new_district = json_data.get('district', '').strip()
+
+                if new_district and new_district not in VALID_DISTRICTS:
+                    errors['district'] = 'Invalid district.'
+                elif new_district and new_district != (user.district or ''):
+                    if user.district_changed_at and timezone.now() < user.district_changed_at + COOLDOWN:
+                        next_date = (user.district_changed_at + COOLDOWN).strftime('%d %b %Y')
+                        errors['district'] = f'District can only be changed once every 6 months. Next change: {next_date}.'
+                    else:
+                        user.district = new_district
+                        user.district_changed_at = timezone.now()
+                        updated_fields.append('district')
+                elif new_district == '' and user.district:
+                    if user.district_changed_at and timezone.now() < user.district_changed_at + COOLDOWN:
+                        next_date = (user.district_changed_at + COOLDOWN).strftime('%d %b %Y')
+                        errors['district'] = f'District can only be changed once every 6 months. Next change: {next_date}.'
+                    else:
+                        user.district = None
+                        user.district_changed_at = timezone.now()
+                        updated_fields.append('district')
 
             # Update state
             if 'state' in json_data:
@@ -318,6 +344,7 @@ class UpdateProfileView(View):
                         'phone_number': user.phone_number,
                         'pincode': user.pincode,
                         'district': user.district,
+                        'district_changed_at': user.district_changed_at.isoformat() if user.district_changed_at else None,
                         'state': user.state,
                         'country': user.country,
                         'place': user.place,