refactor(api): switch to header-based auth for GET requests

- Replace body parsing with header validation for GET endpoints
- Update router to properly handle GET vs POST requests
- Add new ValidateRequestWithHeader function
- Update README to document header requirements

README.md

@@ -68,6 +68,12 @@ All API responses are returned in JSON format:
 }
 ```
 
+**Important Notes:**
+- For **POST** requests: All data is sent in the request body as JSON
+- For **GET** requests: All data is sent in HTTP headers (prefixed with `X-`)
+- All requests require authentication (except `/register` and `/login`)
+- Timestamps are in milliseconds (Unix timestamp)
+
 ---
 
 ### 1. Register User
@@ -269,13 +275,16 @@ You can modify multiple fields at once:
 **Method:** GET  
 **Auth Required:** Yes (token)
 
-**Request:**
-```json
-{
-  "token": "your_token",
-  "timeStamp": 1704067200000
-}
+**Request Headers:**
 ```
+X-Token: your_token
+X-Timestamp: 1704067200000
+```
+
+| Header | Type | Required | Description |
+|--------|------|----------|-------------|
+| X-Token | string | Yes | Authentication token |
+| X-Timestamp | int64 | Yes | Client timestamp in milliseconds |
 
 **Response (admin/superuser):**
 ```json