[FEATURE] Enable Single Session for User safety

[LordNetro]

Describe the feature
Implement a Single Session per User enforcement. Currently, multiple users can log in simultaneously using the same credentials. This feature ensures only one active session is allowed per account.

This is a critical safety requirement for industrial environments. It prevents accidental commands from secondary devices that could endanger the physical integrity of operators working on the machinery.

Describe the solution you'd like

1. Settings: Add a "Single Session" toggle in the system settings with a secondary option to define the Enforcement Mode:
   1.1 Kick Previous: Logging in from a new device automatically invalidates the existing session.
   1.2 Block New: If a session is already active, any new login attempts are rejected until the first user logs out.
2. Logic: The server must track active userIds and their associated tokens/sockets.
3. Action: * In Kick Mode: The previous user is redirected to the login page with the message: "Session closed: logged in from another device."
   3.1 In Block Mode: The new user receives an error: "Login failed: An active session already exists for this account."

Additional context
There is a similar request from 3 years ago:
#1020