fix: restore frontend helpers after merge conflicts

[Simultech369]

Description

Restores frontend helpers and cleans up merge-conflict fallout that left current main with duplicated imports, clipped helper exports, and syntactically broken frontend files.

Changes

• Restores explorerUrl(), bpsToPercent(), formatEventTime(), timeAgo(), and consolidated timestamp formatting helpers.
• Normalizes leaderboard rendering back through LeaderboardTable and removes the duplicate lastUpdated state conflict.
• Cleans up market detail helper imports and renders one event timestamp with formatEventTime().
• Restores syntactically valid event service/tests and aligns the navbar brand test with the rendered StellarPulse text.

Validation

• npm.cmd test -- helpers.test.ts - 59 passed
• npx.cmd tsc --noEmit - passed
• npm.cmd test - 181 passed
• npm.cmd run build - passed

[Simultech369]

I am cleaning up older open PRs on my account. If this repair is no longer needed after the merged leaderboard work, I will close it after a short grace period.

If it is still useful, I am happy to keep it open and update it.

[Muyideen-js]

@Simultech369 fix the conflict

[Muyideen-js]

@Simultech369 fix the file issue

[Simultech369]

Resolved the merge conflicts and file issues cleanly against latest main:

• Deduplicated helper exports in frontend/src/utils/helpers.ts and cleaned up component imports in markets/[id]/page.tsx and leaderboard/page.tsx.
• Revalidated frontend completely: npx tsc --noEmit (0 errors), npm run build (success), npm test (210/210 passed), git diff --check (clean).