[BUG]: Pros & Cons Challenge is Completely Non-Functional (Missing Routes)

[Surajshivam-123]

Bug Description

When opening the Pros & Cons Challenge (/coach/pros-cons) and starting a challenge, the UI shows:
Failed to fetch topic

Root Cause:

• The frontend makes requests to GET /coach/pros-cons/topic and POST /coach/pros-cons/submit.
• neither route was ever wired into Gin in main.go:122-124 or coach.go. The server returns 404
  Not Found.

Steps to Reproduce

1. Go to /coach/pros-cons
2. Select get topic button
3. Error will show "Unexpected non-whitespace character after JSON at position 4 (line 1 column 5)"

Code of Conduct

• I have joined the Discord server and will post updates there
• I have searched existing issues to avoid duplicates

[Surajshivam-123]

@Ri1tik can i work on this issue?