Add Group Profile Picture Upload & Display Feature

[Akash504-ai]

Description

Currently, groups in the application do not support profile pictures.
Users can create groups, but there is no option to:

• Upload a group image during creation
• Edit/update group profile picture later
• Display group avatar in the sidebar

This limits customization and reduces UX consistency compared to individual user profiles.

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Proposed Solution

Implement full group profile picture support.

🔹 Backend

• Add groupImage field to Group model
• Support image upload (Cloudinary / storage service)
• Create API endpoint to update group image
• Validate file type and size

🔹 Frontend

• Add image upload option in:
  • Create Group modal
  • Group settings
• Show group avatar in sidebar list
• Fallback to default icon if no image

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Acceptance Criteria

• Group image can be uploaded during group creation
• Group image can be updated later
• Image persists in database
• Image displays in sidebar and chat header
• Proper validation for image type & size