feat: introduce apply button functionality (v0.1)

### Summary
- Added a new "Apply" button to code snippets provided by the AI assistant.
- The button is designed to seamlessly merge the AI-generated snippet into the relevant file in the editor.

### Current Issues
1. **Sticky Accept/Decline Buttons:** These activate for every snippet instead of being limited to the relevant snippet.
2. **Discard Button:** Currently non-functional.
3. **Highlight Inconsistencies:** The green-red code highlights for old and new code are inconsistent.

### To Do
- Implement a toast notification when the "Apply" button is pressed on an irrelevant tab to prevent code application errors.

### Workflow Implemented
1. The "Apply" button is added alongside "Copy" and "Reply" for AI-generated code snippets.
2. Upon clicking "Apply," the code snippet and relevant file content (active file) are sent to a secondary model (GPT-4O).
3. The system prompt for GPT-4O instructs it to merge the snippet with the file content:
   - Ensure the original file functionality remains intact.
   - Integrate the code snippet seamlessly.
4. The output from GPT-4O is injected directly into the code editor.
5. Changes are visually highlighted:
   - Green for new code.
   - Red for removed code.
6. Highlights remain until the user explicitly accepts or discards the changes.

frontend/package.json

@@ -55,6 +55,7 @@
     "monaco-themes": "^0.4.4",
     "next": "14.1.3",
     "next-themes": "^0.3.0",
+    "openai": "^4.73.1",
     "posthog-js": "^1.147.0",
     "react": "^18.3.1",
     "react-dom": "^18",