feat(backend): migrate resolver utilities to TypeScript (7.17)

[flyblackbox]

Summary

• Migrates all 12 resolver utility modules from legacy JavaScript to TypeScript with full type annotations (issue 7.17)
• Creates 7 Mongoose model stubs (Activity, Post, Vote, Comment, Message, MessageRoom, Notification) needed for compilation — to be expanded in issues 7.19-7.22
• Adds missing deleted/readBy fields to Message type and dayPoints/pointTimestamp to PostDocument
• Stripe utilities use runtime require() with untyped interfaces to avoid adding the stripe dependency prematurely

Files changed (22 files, +805 lines)

New resolver utilities (12):
common.ts, activities.ts, notifications.ts, posts.ts, scores.ts, messages.ts, reputation.ts, stripe/getStripeAuth.ts, stripe/createStripeCustomer.ts, stripe/createStripePaymentMethod.ts, stripe/index.ts, utils/index.ts

New model stubs (7):
Activity.ts, Post.ts, Vote.ts, Comment.ts, Message.ts, MessageRoom.ts, Notification.ts

Modified (3):
models/index.ts, types/common.ts, types/mongoose.ts

Test plan

• pnpm type-check passes clean (0 errors)
• All 224 existing tests pass
• 99.69% code coverage maintained
• Verify model stubs don't conflict with future full model migrations (7.19-7.22)

🤖 Generated with Claude Code

[shubham-01-star]

Hey @flyblackbox ,
I've reviewed the PR and pushed the necessary fixes to complete the backend migration:

Cleaned up the typings and ensured all resolver utilities are strictly typed.
Fixed the remaining gaps in the tests to reach 100% coverage (statements, branches, functions, lines).

[flyblackbox]

Nice work @shubham-01-star! @motirebuma or myself will review and approve soon. Thank you so much 🙏

[flyblackbox]

Excellent job! I found it interesting that there is a trending algorithm still present from an earlier version. Also I love the reputation score bits. Will look for a second review for merge approval

[mzpolini]

hello @shubham-01-star 👋 !

do you advise this merged 1st followed by #301 and #302 ?

I wanted to help review but notice they are touching the same resolver utility test files

[shubham-01-star]

Hey @mzpolini,
Yes, I think we should merge them in order. The PR that came first should be merged first, and then #301 and #302 can follow. Since they touch the same resolver utility test files, merging them sequentially should help avoid conflicts.