Integrate Deutsche Post shipping API and models

Added Deutsche Post as a shipping carrier, including new models, admin, serializers, and API client integration. Updated Carrier and SiteConfiguration models to support Deutsche Post, including shipping price and API credentials. Added requirements for the Deutsche Post API client and dependencies.

backend/account/tokens.py

@@ -20,12 +20,18 @@ password_reset_token = PasswordResetTokenGenerator()
 from rest_framework_simplejwt.authentication import JWTAuthentication
 from rest_framework_simplejwt.exceptions import InvalidToken, TokenError
 
-#NEMĚNIT CUSTOM SBÍRANÍ COOKIE TOKENU
+#COOKIE + AUTHORIZATION HEADER JWT AUTHENTICATION FOR AXIOS COMPATIBILITY
 class CookieJWTAuthentication(JWTAuthentication):
     def authenticate(self, request):
-
+        # First try Authorization header (standard axios pattern)
+        header_token = self.get_header(request)
+        if header_token is not None:
+            validated_token = self.get_validated_token(header_token)
+            return self.get_user(validated_token), validated_token
+        
+        # Fallback to cookie-based authentication
         raw_token = request.COOKIES.get('access_token')
-
+        
         if not raw_token:
             return None