logout

Logs out the user and clears all authentication state.

This method clears:

• Access and refresh tokens

• Stored passkey credential ID (forces fallback to discoverable mode on next auth)

Call this when:

• User explicitly logs out

• Switching between accounts

• After unrecoverable authentication errors

Note: This does NOT delete wallet data or backups. To fully clear all data, use debugClearHotStorage() instead.