feat(app): add two-step confirmation for archive session

[hotic]

What does this PR do?

Closes #7886

How did you verify your code works?

Add two-step confirmation when archiving sessions in WebUI sidebar to prevent accidental data loss.

• First click: button turns red (danger state), tooltip shows "Click to confirm"
• Second click: executes archive action
• Mouse leave: resets confirmation state
• Keyboard shortcut (⌘⇧Backspace) also requires pressing twice

This prevents accidentally archiving sessions with a single misclick.