fix: reject inverted budget ranges with Zod v4 compatibility (#2853)

[oujiesheng]

/claim #743

Summary

Fixes #2853 — adds budget range validation to both createJobSchema and updateJobSchema while maintaining Zod v3 + v4 compatibility.

Root Cause

The original code had no validation that budgetMax >= budgetMin. A naive fix that adds .refine() to createJobSchema and then calls .partial() on it for updateJobSchema crashes in Zod v4:

Error: .partial() cannot be used on object schemas containing refinements

Fix

Extract baseJobFields as a plain Zod object (no refinements), then derive both schemas:

const baseJobFields = z.object({ title, description, budgetMin, budgetMax, categoryId, skills });

export const createJobSchema = baseJobFields.refine(d => d.budgetMax >= d.budgetMin, ...);
export const updateJobSchema = baseJobFields.partial().refine(d => {
  if (d.budgetMin !== undefined && d.budgetMax !== undefined)
    return d.budgetMax >= d.budgetMin;
  return true;
}, ...);

Changes

• apps/api/src/validators/job.js — schema refactor (base/derived separation)
• apps/api/src/tests/job.test.js — 18 tests using node:test (repo convention)

Test Results

node --test apps/api/src/tests/*.test.js
tests 19 | pass 19 | fail 0

Closes #2853