let the year be changeable

app/statistic/templates/statistic/overview.html

@@ -281,6 +281,27 @@
         height: 20px;
         border-radius: 4px;
     }
+    
+    /* Jahr-Navigation */
+    .year-navigation .btn {
+        border-radius: 50%;
+        width: 40px;
+        height: 40px;
+        display: flex;
+        align-items: center;
+        justify-content: center;
+        transition: all 0.3s ease;
+    }
+    
+    .year-navigation .btn:hover:not(:disabled) {
+        background-color: rgba(255, 255, 255, 0.2);
+        transform: scale(1.1);
+    }
+    
+    .year-navigation .btn:disabled {
+        opacity: 0.5;
+        cursor: not-allowed;
+    }
 </style>
 {% endblock %}
 
@@ -295,11 +316,40 @@
             </div>
         </div>
 
-        <!-- 1. Übersicht aktuelles Jahr -->
+        <!-- 1. Übersicht ausgewähltes Jahr mit Navigation -->
-        <div class="section-header">
+        <div class="section-header d-flex justify-content-between align-items-center">
             <h2 class="mb-0">
-                <i class="fas fa-calendar-alt"></i> Übersicht {{ current_year }}
+                <i class="fas fa-calendar-alt"></i> Übersicht {{ selected_year }}
             </h2>
+            <div class="year-navigation d-flex align-items-center">
+                {% if can_go_previous %}
+                    <a href="?year={{ previous_year }}" class="btn btn-outline-light me-2" title="Vorheriges Jahr ({{ previous_year }})">
+                        <i class="fas fa-chevron-left"></i>
+                    </a>
+                {% else %}
+                    <button class="btn btn-outline-light me-2" disabled title="Keine Daten vor {{ earliest_year }}">
+                        <i class="fas fa-chevron-left"></i>
+                    </button>
+                {% endif %}
+                
+                <span class="mx-3 fw-bold">{{ selected_year }}</span>
+                
+                {% if can_go_next %}
+                    <a href="?year={{ next_year }}" class="btn btn-outline-light ms-2" title="Nächstes Jahr ({{ next_year }})">
+                        <i class="fas fa-chevron-right"></i>
+                    </a>
+                {% else %}
+                    <button class="btn btn-outline-light ms-2" disabled title="Aktuelles Jahr erreicht">
+                        <i class="fas fa-chevron-right"></i>
+                    </button>
+                {% endif %}
+                
+                {% if selected_year != current_year %}
+                    <a href="?year={{ current_year }}" class="btn btn-light ms-3" title="Zurück zu {{ current_year }}">
+                        <i class="fas fa-calendar-day me-1"></i>{{ current_year }}
+                    </a>
+                {% endif %}
+            </div>
         </div>
         
         <div class="row g-4 mb-4">
@@ -441,7 +491,7 @@
                 <div class="col-md-6">
                     <div class="card">
                         <div class="card-header">
-                            <h5 class="mb-0">{{ current_year }}</h5>
+                            <h5 class="mb-0">{{ selected_year }}</h5>
                         </div>
                         <div class="card-body">
                             {% if circumstances_this_year %}
@@ -456,7 +506,7 @@
                                 </div>
                             {% else %}
                                 <div class="text-center text-muted">
-                                    <p>Keine Daten für {{ current_year }} verfügbar</p>
+                                    <p>Keine Daten für {{ selected_year }} verfügbar</p>
                                 </div>
                             {% endif %}
                         </div>
@@ -516,6 +566,37 @@ document.addEventListener('DOMContentLoaded', function() {
             }
         }
     });
+    
+    // Tastatur-Navigation für Jahre
+    document.addEventListener('keydown', function(e) {
+        // Nur reagieren wenn kein Input-Element fokussiert ist
+        if (document.activeElement.tagName === 'INPUT' || document.activeElement.tagName === 'TEXTAREA') {
+            return;
+        }
+        
+        if (e.key === 'ArrowLeft') {
+            // Vorheriges Jahr
+            const prevButton = document.querySelector('a[href*="year={{ previous_year }}"]');
+            if (prevButton) {
+                window.location.href = prevButton.href;
+            }
+        } else if (e.key === 'ArrowRight') {
+            // Nächstes Jahr
+            const nextButton = document.querySelector('a[href*="year={{ next_year }}"]');
+            if (nextButton) {
+                window.location.href = nextButton.href;
+            }
+        } else if (e.key === 'Home') {
+            // Zurück zum aktuellen Jahr
+            const currentYearButton = document.querySelector('a[href*="year={{ current_year }}"]');
+            if (currentYearButton) {
+                window.location.href = currentYearButton.href;
+            } else {
+                // Falls schon im aktuellen Jahr, zur Statistik-Hauptseite
+                window.location.href = window.location.pathname;
+            }
+        }
+    });
 });
 </script>
 {% endblock %}

app/statistic/views.py

@@ -1,6 +1,6 @@
 from django.views.generic import TemplateView
 from django.contrib.auth.mixins import LoginRequiredMixin
-from django.db.models import Count, Q
+from django.db.models import Count, Q, Min
 from django.utils import timezone
 from datetime import datetime
 from bird.models import FallenBird, Bird, BirdStatus, Circumstance
@@ -13,9 +13,31 @@ class StatisticView(LoginRequiredMixin, TemplateView):
     def get_context_data(self, **kwargs):
         context = super().get_context_data(**kwargs)
         
-        # Aktuelles Jahr
+        # Jahr aus URL-Parameter oder aktuelles Jahr
+        selected_year = self.request.GET.get('year', timezone.now().year)
+        try:
+            selected_year = int(selected_year)
+        except (ValueError, TypeError):
+            selected_year = timezone.now().year
+        
         current_year = timezone.now().year
         
+        # Stelle sicher, dass das ausgewählte Jahr nicht in der Zukunft liegt
+        if selected_year > current_year:
+            selected_year = current_year
+        
+        # Finde das früheste Jahr mit Daten
+        earliest_year_with_data = FallenBird.objects.aggregate(
+            earliest=Min('date_found__year')
+        )['earliest']
+        
+        if earliest_year_with_data is None:
+            earliest_year_with_data = current_year
+        
+        # Stelle sicher, dass das ausgewählte Jahr nicht vor dem frühesten Jahr liegt
+        if selected_year < earliest_year_with_data:
+            selected_year = earliest_year_with_data
+        
         # Lade aktive Konfiguration
         try:
             config = StatisticConfiguration.objects.get(is_active=True)
@@ -31,11 +53,17 @@ class StatisticView(LoginRequiredMixin, TemplateView):
         
         context['config'] = config
         context['current_year'] = current_year
+        context['selected_year'] = selected_year
+        context['earliest_year'] = earliest_year_with_data
+        context['can_go_previous'] = selected_year > earliest_year_with_data
+        context['can_go_next'] = selected_year < current_year
+        context['previous_year'] = selected_year - 1 if context['can_go_previous'] else None
+        context['next_year'] = selected_year + 1 if context['can_go_next'] else None
         
         # 1. Jahresstatistik
         if config.show_year_total_patients:
             patients_this_year = FallenBird.objects.filter(
-                date_found__year=current_year
+                date_found__year=selected_year
             ).count()
             context['patients_this_year'] = patients_this_year
         
@@ -46,7 +74,7 @@ class StatisticView(LoginRequiredMixin, TemplateView):
         for group in year_groups:
             status_ids = list(group.status_list.values_list('id', flat=True))
             year_count = FallenBird.objects.filter(
-                date_found__year=current_year,
+                date_found__year=selected_year,
                 status__id__in=status_ids
             ).count()
             
@@ -144,10 +172,10 @@ class StatisticView(LoginRequiredMixin, TemplateView):
         
         context['bird_stats'] = bird_stats
         
-        # 4. Fundumstände-Statistiken (unverändert)
+        # 4. Fundumstände-Statistiken
-        # Fundumstände für aktuelles Jahr
+        # Fundumstände für ausgewähltes Jahr
         circumstances_this_year = FallenBird.objects.filter(
-            date_found__year=current_year,
+            date_found__year=selected_year,
             find_circumstances__isnull=False
         ).values('find_circumstances__name', 'find_circumstances__description').annotate(
             count=Count('id')