feat(follow): implement complete follow/unfollow functionality

[Samm-05]

📌 Overview

This pull request implements the complete Follow / Unfollow functionality for DevLink, enabling users to follow other builders, manage follower relationships, and view follow statistics.

Closes <#120>

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✨ Features Implemented

Backend

• Added Follow API endpoints

  • POST /users/{user_id}/follow
  • DELETE /users/{user_id}/follow
  • GET /users/{user_id}/followers
  • GET /users/{user_id}/following
  • GET /users/{user_id}/follow-status

• Prevented duplicate follow requests.

• Prevented users from following themselves.

• Automatically updates follower and following counts.

• Preserved backward compatibility with existing /followers/* routes.

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Frontend

• Added reusable FollowButton component.

• Integrated Follow/Unfollow functionality into builder/profile pages.

• Added optimistic UI updates using TanStack React Query.

• Added loading and disabled states during API requests.

• Synced follower counts automatically after follow/unfollow actions.

• Connected frontend services to the new backend endpoints.

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🧩 Additional Improvements

• Fixed TypeScript build issues discovered during implementation.

• Fixed import inconsistencies.

• Cleaned JSX nesting issues causing frontend compilation failures.

• Improved overall API consistency.

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✅ Validation

Successfully verified:

• ✅ Backend compilation
• ✅ Frontend production build
• ✅ TypeScript type checking
• ✅ API integration
• ✅ Follow/Unfollow workflow
• ✅ Optimistic updates
• ✅ No database migration required

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🧪 Testing Performed

• Follow another user
• Unfollow a user
• Duplicate follow prevention
• Self-follow prevention
• Follow status endpoint
• Followers list
• Following list
• Optimistic UI updates
• Loading states
• Error handling

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📂 Files Changed

Backend

• Follow router
• Follow schemas
• Follow service
• API endpoint updates

Frontend

• FollowButton component
• React Query hooks
• API service
• Profile integration
• Builder pages

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🚀 Notes

• No breaking changes.
• No database migration required.
• Existing functionality remains unaffected.
• Implementation follows the existing project architecture and coding standards.

[nensii21]

attach screenshots and videos showing what changes have been made. Also CI jobs are failing so please update it.