Add Zod dependency and update API interfaces

- Added Zod as a dependency in package.json.
- Updated pnpm-lock.yaml to include Zod.
- Refactored API interfaces: exported new modules for perk, survivor, mission, and encounter.
- Removed obsolete api-interfaces.ts file.
- Enhanced tests for new schemas in api-interfaces.spec.ts, covering various validation scenarios.

package.json

@@ -70,6 +70,7 @@
     "@nestjs/platform-express": "^11.0.0",
     "axios": "^1.6.0",
     "reflect-metadata": "^0.1.13",
-    "rxjs": "^7.8.0"
+    "rxjs": "^7.8.0",
+    "zod": "^4.4.3"
   }
 }