Feature Request: Profile Image Upload (Local File Support)

### Summary

Currently, users can only choose profile avatars from preset DiceBear options. This issue proposes adding support for uploading a custom profile image from the local device, stored and served by the backend.

### Goal

Allow authenticated users to upload a JPG/PNG profile image, save it on the backend, and immediately display it in the UI with persistence across refreshes.

### Backend Changes
** New Controller**
```
File: backend/controllers/upload_controller.go
Function: UploadAvatar(c *gin.Context)
```

### Responsibilities:

1. Accept multipart file upload
2. Enforce max file size: 5MB
3. Validate file types: .jpg, .jpeg, .png
4. Save file to: ./uploads/avatars/
5. Return public URL:

> http://localhost:1313/uploads/avatars/

### Server Setup

_**File: backend/cmd/server/main.go**_

**Serve uploads directory statically:**

router.Static("/uploads", "./uploads")

**Register protected route:**

_auth.POST("/user/upload-avatar", controllers.UploadAvatar)_

⚠️ Note: Ensure uploads/avatars exists and backend has write permissions.

### Frontend Changes
#### **Profile Service**
```
File: frontend/src/services/profileService.ts
```

1. Add uploadAvatar(token, file) method
2. Use FormData
3. POST to /user/upload-avatar
4. Return uploaded avatar URL

#### **Profile Page UI**

_File: frontend/src/Pages/Profile.tsx_

1. Add hidden
2. Add an Upload Avatar button (or camera icon)
3. On file selection:

> - Call uploadAvatar
> - Update avatar URL in state
> - Reflect change immediately in UI

### Verification Plan
Backend

**1. Test with Postman:**
```
POST /user/upload-avatar

```
2. Confirm file saved in backend/uploads/avatars/
3. Confirm API returns valid public URL

**Frontend**

1. Login → Profile page
2. Click Upload Avatar
3. Select JPG/PNG image
4. Avatar updates instantly
5. Refresh page → avatar persists

**Labels (suggested)**

feature
frontend
backend
enhancement