many fixes of backeend and fronteend

backend/igny8_core/modules/billing/admin.py

@@ -2,7 +2,9 @@
 Billing Module Admin
 """
 from django.contrib import admin
+from django.utils.html import format_html
 from igny8_core.admin.base import AccountAdminMixin
+from igny8_core.business.billing.models import CreditCostConfig
 from .models import CreditTransaction, CreditUsageLog, AccountPaymentMethod
 
 
@@ -70,3 +72,78 @@ class AccountPaymentMethodAdmin(AccountAdminMixin, admin.ModelAdmin):
         }),
     )
 
+
+@admin.register(CreditCostConfig)
+class CreditCostConfigAdmin(admin.ModelAdmin):
+    list_display = [
+        'operation_type',
+        'display_name',
+        'credits_cost_display',
+        'unit',
+        'is_active',
+        'cost_change_indicator',
+        'updated_at',
+        'updated_by'
+    ]
+    
+    list_filter = ['is_active', 'unit', 'updated_at']
+    search_fields = ['operation_type', 'display_name', 'description']
+    
+    fieldsets = (
+        ('Operation', {
+            'fields': ('operation_type', 'display_name', 'description')
+        }),
+        ('Cost Configuration', {
+            'fields': ('credits_cost', 'unit', 'is_active')
+        }),
+        ('Audit Trail', {
+            'fields': ('previous_cost', 'updated_by', 'created_at', 'updated_at'),
+            'classes': ('collapse',)
+        }),
+    )
+    
+    readonly_fields = ['created_at', 'updated_at', 'previous_cost']
+    
+    def credits_cost_display(self, obj):
+        """Show cost with color coding"""
+        if obj.credits_cost >= 20:
+            color = 'red'
+        elif obj.credits_cost >= 10:
+            color = 'orange'
+        else:
+            color = 'green'
+        return format_html(
+            '<span style="color: {}; font-weight: bold;">{} credits</span>',
+            color,
+            obj.credits_cost
+        )
+    credits_cost_display.short_description = 'Cost'
+    
+    def cost_change_indicator(self, obj):
+        """Show if cost changed recently"""
+        if obj.previous_cost is not None:
+            if obj.credits_cost > obj.previous_cost:
+                icon = '📈'  # Increased
+                color = 'red'
+            elif obj.credits_cost < obj.previous_cost:
+                icon = '📉'  # Decreased
+                color = 'green'
+            else:
+                icon = '➡️'  # Same
+                color = 'gray'
+            
+            return format_html(
+                '{} <span style="color: {};">({} → {})</span>',
+                icon,
+                color,
+                obj.previous_cost,
+                obj.credits_cost
+            )
+        return '—'
+    cost_change_indicator.short_description = 'Recent Change'
+    
+    def save_model(self, request, obj, form, change):
+        """Track who made the change"""
+        obj.updated_by = request.user
+        super().save_model(request, obj, form, change)
+