feat: add gfg integration

[Devx2107]

# feat: add GeeksForGeeks platform integration

What

Adds GeeksForGeeks as a 5th platform, raising the maximum total score from 4000 to 5000.

Why

GFG is heavily used by NSUT students for placement prep — DSA practice, company-specific problem sets, and the GFG Institute Rank are all things students actively track. It was a visible gap in the leaderboard for anyone doing placement-focused practice alongside competitive programming.

Changes

New file — backend/platforms/gfg.js

Full platform module following the existing registry contract:

• fetchStats(username) — hits GFG's internal JSON API (auth.geeksforgeeks.org/user/{username}/practice/). No scraping — GFG returns structured JSON directly, making this more reliable than the existing CodeChef integration.
• validateUsername(username) — checks for a valid userHandle in the API response
• calculateScore(stats) — weighted solved score (Easy×1 + Med×3 + Hard×6, max 700) + GFG practice score bonus (max 300), capped at 1000. Same shape as the LeetCode formula.
• Tracks 8 stats: totalSolved, easySolved, mediumSolved, hardSolved, score, monthlyScore, instituteRank, streak

backend/platforms/index.js

• Added require('./gfg') and registered it in the platforms array

backend/models/Student.js

• Added gfg subdocument (username + 8 stats fields + lastUpdated)
• Added scores.gfg and ranks.gfg fields
• Existing documents unaffected — Mongoose defaults handle the missing fields gracefully until next cron run

backend/controllers/studentController.js

• Changed PLATFORM_KEYS from a hardcoded array to getAllPlatforms().map(p => p.key) so new platforms are automatically picked up without manual edits here

backend/cron/updateData.js

• Added gfg to PLATFORM_CONCURRENCY (4 workers) and PLATFORM_DELAY_MS (300ms)

README.md

• Added GFG row to the Scoring System table
• Added GFG row to the Data Update Pipeline table
• Updated max total score reference from 4000 → 5000
• Added gfg.js to the project structure

No new dependencies

axios already handles the JSON API calls. No scraping libraries needed.

Testing

• Validated against real GFG profiles — fetchStats returns correct solved counts and score
• validateUsername correctly returns false for non-existent usernames (404 from GFG API)
• Registered a test student with a GFG username — stats fetched on registration, score calculated, leaderboard rank updated correctly
• Cron run picks up GFG alongside existing platforms with no interference

Notes

• GFG's API is unofficial (used by their own site) but has been stable for a long time. If it ever breaks, fetchStats returns null gracefully and the cron skips that student's GFG data without affecting other platforms.
• instituteRank will reflect the student's college rank if they've set their institute to NSUT on their GFG profile — useful signal for placement context.
• monthlyScore is worth surfacing in a future PR as a "This Month" leaderboard column — left out of this PR to keep scope tight.
• GFG doesn't expose a submission calendar API, so no heatmap support — consistent with CodeChef's current behavior.

[sujallchaudhary]

is the new platform really required?

[Devx2107]

is the new platform really required?

I think so its a nice little addition as quite a few begginers begin their journey from gfg . Also i think we can add atcoder as well. Instead of them getting a big sillhoute on the main page . it can be give space only when you open the profile and that too at the bottom of all of it.

[sujallchaudhary]

yes it's better to add these small platforms on profile page
instead of changing whole leaderboard.

sorry for late reply :)

[Devx2107]

yes it's better to add these small platforms on profile page instead of changing whole leaderboard.

sorry for late reply :)

hmm true , its okay happens no issues