refactor: move event handlers from simple-modals to respective files (@biplavbarua)

[biplavbarua]

This PR addresses the TODO in simple-modals.ts by moving event handlers to their respective page controller files (account-settings.ts and settings.ts).

Key Changes:

1. Moved .pageAccountSettings handlers to account-settings.ts.
2. Moved .pageSettings handlers to settings.ts.
3. Extracted PopupKey, list, and showPopup to simple-modals-base.ts to resolve circular dependencies introduced by importing page controllers in simple-modals.ts (which now import showPopup from base).

Testing:

• Verified no circular dependencies with madge.
• Verified type safety with tsc.
• Verified build success.