feat(feedback): Add content improvement feedback system

Frontend (frontend/app.js):

- Add textarea for improvement feedback

- Add submit button with loading state

- Handle API response and display improved content

Backend (backend/copywriter.py):

- Add improve_copy() method using Cohere API

- Integrate retry mechanism for API calls

Backend (backend/main.py):

- Add /improve-content POST endpoint

- Implement error handling and return improved content with metadata

Testing:

- Verified feedback submission flow

- Confirmed improved content generation

- Tested error scenarios and loading states

docs/API_DOCUMENTATION.md

@@ -15,7 +15,6 @@ Generates marketing copy based on the provided prompt and optional parameters.
 {
   "prompt": "Write a social media post for our new product launch",
   "content_type": "social_media",
-  "tone": "excited",
   "length": "medium",
   "include_cta": true
 }
@@ -24,7 +23,6 @@ Generates marketing copy based on the provided prompt and optional parameters.
 **Parameters**:
 - `prompt` (string, required): The main instruction for generating content
 - `content_type` (string, optional): Type of content to generate (social_media, email, blog, website, etc.)
-- `tone` (string, optional): Desired tone (excited, professional, casual, etc.)
 - `length` (string, optional): Content length (short, medium, long)
 - `include_cta` (boolean, optional): Whether to include a call to action
 
@@ -184,4 +182,4 @@ Error response format:
   "message": "Detailed error message",
   "error_code": "ERROR_CODE"
 }
-```
+```