Add Remember Me session storage for login

[gTanusri]

Summary

• Added a shared auth storage helper to support both persistent and session-only login.
• Added a Remember Me checkbox on the login page.
• Store auth tokens in localStorage when Remember Me is checked and sessionStorage when unchecked.
• Applied the same storage behavior to Google login.
• Updated protected routes, API interceptors, logout, and websocket notification requests to read and clear auth data from both storage locations.
• Fixed a missing closing brace in ApiService.js that was preventing the frontend build from parsing.

Issue

Closes #242

Validation

• npm run build passes
• ./gradlew.bat compileJava passes
• git diff --check passes