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/class/equality.wren

@@ -0,0 +1,13 @@
+io.write(Num == Num)  // expect: true
+io.write(Num == Bool) // expect: false
+
+// Not equal to other types.
+io.write(Num == 123)  // expect: false
+io.write(Num == true) // expect: false
+
+io.write(Num != Num)  // expect: false
+io.write(Num != Bool) // expect: true
+
+// Not equal to other types.
+io.write(Num != 123)  // expect: true
+io.write(Num != true) // expect: true