feat: Add price formatting filter and update invoice templates for improved display

backend/order/templatetags/price_filters.py

@@ -0,0 +1,18 @@
+from django import template
+
+register = template.Library()
+
+
+@register.filter(name='price_format')
+def price_format(value):
+    """
+    Format a number with thousand separators (commas).
+    Example: 1234567 -> 1,234,567
+    """
+    try:
+        # Convert to int to remove decimals
+        value = int(float(value))
+        # Format with thousand separators
+        return "{:,}".format(value)
+    except (ValueError, TypeError):
+        return value