Add management commands for semester deadline migration

- add update_semester_deadlines: Update quarterly deadlines to semester-based system
- add check_deadlines: Check current deadline status and validation
- includes dry-run mode and year filtering options
- provides clear progress feedback and summaries

Usage on VPS after GitHub Action deployment:
  python manage.py check_deadlines
  python manage.py update_semester_deadlines --dry-run
  python manage.py update_semester_deadlines

app/stiftung/management/commands/check_deadlines.py

@@ -0,0 +1,77 @@
+from django.core.management.base import BaseCommand
+from collections import defaultdict
+from stiftung.models import VierteljahresNachweis
+
+
+class Command(BaseCommand):
+    help = 'Check current quarterly confirmation deadline status'
+
+    def add_arguments(self, parser):
+        parser.add_argument(
+            '--year',
+            type=int,
+            help='Check deadlines for specific year (default: current and next year)',
+        )
+
+    def handle(self, *args, **options):
+        from datetime import date
+        
+        year_filter = options['year']
+        current_year = date.today().year
+        
+        if year_filter:
+            years_to_check = [year_filter]
+        else:
+            years_to_check = [current_year, current_year + 1]
+        
+        self.stdout.write('Current Quarterly Confirmation Deadline Status')
+        self.stdout.write('=' * 50)
+        
+        for year in years_to_check:
+            self.stdout.write(f'\nYear: {year}')
+            self.stdout.write('-' * 20)
+            
+            deadlines_by_quarter = defaultdict(set)
+            status_by_quarter = defaultdict(list)
+            
+            records = VierteljahresNachweis.objects.filter(jahr=year).order_by('quartal', 'destinataer__nachname')
+            
+            if not records:
+                self.stdout.write('  No records found for this year')
+                continue
+                
+            for record in records:
+                deadlines_by_quarter[record.quartal].add(record.faelligkeitsdatum)
+                status_by_quarter[record.quartal].append(record.status)
+            
+            # Show deadline summary
+            expected_deadlines = {
+                1: f'{year}-03-15',  # March 15
+                2: f'{year}-06-15',  # June 15
+                3: f'{year}-09-15',  # September 15
+                4: f'{year}-12-15',  # December 15
+            }
+            
+            for quarter in sorted(deadlines_by_quarter.keys()):
+                unique_deadlines = list(deadlines_by_quarter[quarter])
+                expected = expected_deadlines[quarter]
+                record_count = len([s for s in status_by_quarter[quarter]])
+                
+                if len(unique_deadlines) == 1 and str(unique_deadlines[0]) == expected:
+                    status_icon = self.style.SUCCESS('✓')
+                    status_text = 'CORRECT'
+                else:
+                    status_icon = self.style.ERROR('✗')
+                    status_text = 'NEEDS UPDATE'
+                
+                self.stdout.write(f'  Q{quarter}: {status_icon} {unique_deadlines[0]} (expected: {expected}) - {record_count} records - {status_text}')
+        
+        self.stdout.write('\nExpected semester-based deadline structure:')
+        self.stdout.write('  Q1: March 15   (Primary semester submission)')
+        self.stdout.write('  Q2: June 15    (Auto-approved when Q1 approved)')  
+        self.stdout.write('  Q3: September 15 (Primary semester submission)')
+        self.stdout.write('  Q4: December 15  (Auto-approved when Q3 approved)')
+        
+        self.stdout.write(f'\nTo update deadlines, run:')
+        self.stdout.write(f'  python manage.py update_semester_deadlines --dry-run  # Preview changes')
+        self.stdout.write(f'  python manage.py update_semester_deadlines           # Apply changes')

app/stiftung/management/commands/update_semester_deadlines.py

@@ -0,0 +1,95 @@
+from django.core.management.base import BaseCommand
+from django.db import transaction
+from datetime import date
+from stiftung.models import VierteljahresNachweis
+
+
+class Command(BaseCommand):
+    help = 'Update quarterly confirmation deadlines to semester-based system'
+
+    def add_arguments(self, parser):
+        parser.add_argument(
+            '--dry-run',
+            action='store_true',
+            help='Show what would be updated without making changes',
+        )
+        parser.add_argument(
+            '--year',
+            type=int,
+            help='Only update records for specific year (default: all years)',
+        )
+
+    def handle(self, *args, **options):
+        dry_run = options['dry_run']
+        year_filter = options['year']
+        
+        if dry_run:
+            self.stdout.write(
+                self.style.WARNING('DRY RUN MODE - No changes will be made')
+            )
+        
+        # Filter queryset based on year if provided
+        queryset = VierteljahresNachweis.objects.all()
+        if year_filter:
+            queryset = queryset.filter(jahr=year_filter)
+            self.stdout.write(f'Filtering records for year: {year_filter}')
+        
+        updated_count = 0
+        total_count = queryset.count()
+        
+        self.stdout.write(f'Processing {total_count} quarterly confirmation records...')
+        
+        with transaction.atomic():
+            for nachweis in queryset:
+                # Calculate new semester-based deadlines
+                quarter_deadlines = {
+                    1: date(nachweis.jahr, 3, 15),   # Q1 deadline: March 15 (Spring semester)
+                    2: date(nachweis.jahr, 6, 15),   # Q2 deadline: June 15 (auto-approved)
+                    3: date(nachweis.jahr, 9, 15),   # Q3 deadline: September 15 (Fall semester)
+                    4: date(nachweis.jahr, 12, 15),  # Q4 deadline: December 15 (auto-approved)
+                }
+                
+                new_deadline = quarter_deadlines.get(nachweis.quartal)
+                
+                if new_deadline and nachweis.faelligkeitsdatum != new_deadline:
+                    old_deadline = nachweis.faelligkeitsdatum
+                    
+                    if not dry_run:
+                        nachweis.faelligkeitsdatum = new_deadline
+                        nachweis.save(update_fields=['faelligkeitsdatum'])
+                    
+                    updated_count += 1
+                    
+                    # Show progress for every 10 updates or if verbose
+                    if updated_count % 10 == 0 or options['verbosity'] >= 2:
+                        self.stdout.write(
+                            f'  {nachweis.destinataer.get_full_name()}: '
+                            f'{nachweis.jahr} Q{nachweis.quartal}: '
+                            f'{old_deadline} → {new_deadline}'
+                        )
+        
+        # Summary
+        if dry_run:
+            self.stdout.write(
+                self.style.SUCCESS(
+                    f'DRY RUN: Would update {updated_count} out of {total_count} records'
+                )
+            )
+        else:
+            self.stdout.write(
+                self.style.SUCCESS(
+                    f'Successfully updated {updated_count} out of {total_count} records'
+                )
+            )
+        
+        if updated_count == 0:
+            self.stdout.write(
+                self.style.WARNING('No records needed updating - all deadlines already correct')
+            )
+        else:
+            # Show the new deadline structure
+            self.stdout.write('\nNew semester-based deadline structure:')
+            self.stdout.write('  Q1: March 15   (Primary semester submission)')
+            self.stdout.write('  Q2: June 15    (Auto-approved when Q1 approved)')
+            self.stdout.write('  Q3: September 15 (Primary semester submission)')
+            self.stdout.write('  Q4: December 15  (Auto-approved when Q3 approved)')