bug: StatsSchema zod validation error (#1267)

## Description:

Fix a bug in the StatsSchema zod validation logic. In zod v4, the
`record` function has been renamed to `partialRecord`, and the new
`record` function requires that all keys are present. We intentionally
omit empty stats, so this causes a zod validation error.

Example error:

```
Connection error!
 game id: VSEtmKpJ, client id: 0UMrA84F
Error: ✖ Invalid input: expected array, received undefined
  → at allPlayersStats.0UMrA84F.units.wshp
✖ Invalid input: expected array, received undefined
  → at allPlayersStats.0UMrA84F.units.saml
Stack: 
```

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced
- [x] I understand that submitting code with bugs that could have been
caught through manual testing blocks releases and new features for all
contributors

tests/StatsSchema.test.ts

@@ -0,0 +1,48 @@
+import { PlayerStatsSchema } from "../src/core/StatsSchemas";
+
+function testPlayerSchema(
+  json: string,
+  expectSuccess = true,
+  expectThrow = false,
+): void {
+  const parse = () => {
+    const raw = JSON.parse(json);
+    const result = PlayerStatsSchema.safeParse(raw);
+    return result.success;
+  };
+
+  if (expectSuccess) {
+    // Expect success
+    expect(parse()).toBeTruthy();
+  } else if (!expectThrow) {
+    // Expect failure
+    expect(parse()).toBeFalsy();
+  } else {
+    // Expect throw
+    expect(parse).toThrow();
+  }
+}
+
+describe("StatsSchema", () => {
+  test("Parse empty", () => {
+    testPlayerSchema("{}");
+  });
+
+  test("Parse partial", () => {
+    testPlayerSchema('{"units":{"port":["0","0","0","1"]}}');
+  });
+
+  test("Parse invalid", () => {
+    testPlayerSchema("[]", false);
+    testPlayerSchema("null", false);
+    testPlayerSchema('"null"', false);
+    testPlayerSchema('"undefined"', false);
+  });
+
+  test("Parse failure", () => {
+    testPlayerSchema("", false, true);
+    testPlayerSchema("undefined", false, true);
+    testPlayerSchema("{", false, true);
+    testPlayerSchema("{}}", false, true);
+  });
+});