feat(rematch): Add synchronized rematch functionality with both player ready-up and optional same-seed

[Russolves]

This PR adds a rematch flow to the multiplayer end-game screen.

So after a match ends:

• Both players can toggle Rematch ready via a button
• UI shows live readiness count status for both players (0/2) -> (1/2) -> (2/2)
• Match host has the ability to toggle whether rematch would be in Same Seed (default: Off)
• When both players are ready, host commits rematch and both clients automatically start a new match with the same lobby/ruleset config (and same seed only if enabled)

Note:

• Locale only supports en-us via en-us.lua currently