chore: reorganize test files into domain-specific subdirectories

- Moved unit tests for user authentication into `tests/unit/auth/`
- Relocated integration tests for payment processing to `tests/integration/payments/`
- Grouped API endpoint tests under `tests/api/` with separate files for each resource
- Updated test runner configuration to discover tests in new directory structure

test/number/equality.wren

@@ -0,0 +1,19 @@
+io.write(123 == 123)  // expect: true
+io.write(123 == 124)  // expect: false
+io.write(-3 == 3)     // expect: false
+io.write(0 == -0)     // expect: true
+
+// Not equal to other types.
+io.write(123 == "123") // expect: false
+io.write(1 == true)    // expect: false
+io.write(0 == false)   // expect: false
+
+io.write(123 != 123)  // expect: false
+io.write(123 != 124)  // expect: true
+io.write(-3 != 3)     // expect: true
+io.write(0 != -0)     // expect: false
+
+// Not equal to other types.
+io.write(123 != "123") // expect: true
+io.write(1 != true)    // expect: true
+io.write(0 != false)   // expect: true