Add OpenAI GPT-5.4 and GPT-5 pricing

Author: DataGomes

backend/core/provider_pricing.json

@@ -274,6 +274,14 @@
     }
   },
   "openai": {
+    "gpt-5.4": {
+      "input": 2.5,
+      "output": 15.0
+    },
+    "gpt-5": {
+      "input": 1.25,
+      "output": 10.0
+    },
     "gpt-4o": {
       "input": 2.5,
       "output": 10.0