Improve hidden message display formatting

- Wrap extracted message in code block for better visibility
- Add clear section headers with markdown H2
- Add horizontal rules for better visual separation
- Make it clearer where the extracted message appears
- Improves UX for Extract Data tab

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

app.py

@@ -233,18 +233,22 @@ def extract_hidden_data(image, password, bits_per_channel):
         result = f"""
 ✅ **Data Successfully Extracted!**
 
-📝 **Hidden Message:**
-
 ---
+
+## 📝 Hidden Message:
+
+```
 {extracted_data}
+```
+
 ---
 
-📊 **Extraction Info:**
+## 📊 Extraction Info:
 - **Data size:** {len(extracted_data)} characters
 - **Decryption:** {"🔒 Used" if pwd else "🔓 Not needed"}
 - **LSB depth:** {bits_per_channel} bit(s) per channel
 
-💡 Copy the message above - it has been successfully recovered from the image!
+💡 **The message is shown in the code block above** - it has been successfully recovered from the image!
 """
         return result