Add user-friendly error messages for 401/403/500 errors

src/ui/handlers.py

@@ -19,12 +19,18 @@ def format_error(error: Exception) -> str:
     msg = str(error)
 
     # Translate common errors
+    if "401" in msg or "unauthorized" in msg.lower():
+        return "Invalid API key. Please check your StackNet Key in the Settings section."
+    if "403" in msg or "forbidden" in msg.lower():
+        return "Access denied. Your API key may not have permission for this operation."
     if "timeout" in msg.lower():
         return "The operation timed out. Please try again with a simpler prompt."
     if "network" in msg.lower() or "connection" in msg.lower():
         return "Network error. Please check your connection and try again."
     if "rate limit" in msg.lower() or "429" in msg.lower():
         return "Too many requests. Please wait a moment and try again."
+    if "500" in msg or "internal server error" in msg.lower():
+        return "Server error. The service is temporarily unavailable. Please try again later."
 
     return f"Error: {msg}"