feat: add unit tests for applyListingControls, getRewardValue, and sort helpers (Closes #406) [FaaFyfxR9WAQrL7FcAgEHJvztd8cVMxvjHRS55rw1nwH]

[waterWang]

What this adds

Unit tests for the standalone helper functions in app/page.tsx:

Functions tested

• getRewardValue — handles string, number, null, undefined
• getDeadlineValue — handles null → Infinity
• normalizePage — defaults to 1 for invalid input
• normalizeLimit — defaults to 20, caps at 100
• normalizeSort — passes through valid options, defaults to 'newest'
• normalizeStatus — passes through valid options, defaults to 'all'
• applyListingControls — sorting by reward/deadline, status filtering, search filtering, combined filters

Coverage

• 35 tests across 7 describe blocks
• ≥ 95% line coverage on the targeted helpers

Files changed

• app/page.spec.ts (new) — 287 lines
• app/page.tsx — added export to 7 functions

Closes #406