feat: add smoke tests, agent credit ledger, and player cashback page

Introduce admin smoke-test suite with API probes, agent credit transaction history, and player cashback records; fix SmokeTestModule DI and polish admin/player UI assets.

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/api/src/shared/uploads/upload-paths.ts

@@ -0,0 +1,16 @@
+import { existsSync } from 'fs';
+import { resolve } from 'path';
+
+export function getUploadRoot() {
+  if (process.env.UPLOAD_DIR?.trim()) {
+    return resolve(process.env.UPLOAD_DIR.trim());
+  }
+
+  const candidates = [
+    resolve(process.cwd(), '..', '..', 'uploads'),
+    resolve(process.cwd(), 'uploads'),
+    resolve(__dirname, '..', '..', 'uploads'),
+  ];
+
+  return candidates.find((p) => existsSync(p)) ?? candidates[0];
+}