feat(WG): lock players to their assigned team for the war

[Nyeriah]

Changes Proposed

Locks a Wintergrasp cross-faction player to the team they were first assigned for the duration of a war.

Previously, players could re-roll their faction by dropping out of the war and rejoining. Team assignment was recomputed on every OnBattlefieldPlayerJoinWar, and the only guard skipped already-faked players. That left two gaps:

• Native-team assignees were never recorded, so they were re-balanced on every join and could be flipped to the opposite faction.
• Faked players reset once they left the zone (the fake is cleared in OnPlayerUpdateZone), so re-entering and re-queuing re-rolled them too.

Fix

A GUID-keyed, per-war assignment store records each player's first WG team. On subsequent joins the stored team is reused instead of re-balancing, so the assignment survives:

• dropping out of the war and rejoining,
• leaving and re-entering the zone,
• relogging during the war.

The store is cleared when the war ends (in OnBattlefieldWarEnd), so the next war balances from scratch and stale entries can't accumulate. GUID keying (not Player*) keeps the lock valid across reconnects.

Config

Gated behind a new option CFBG.Battlefield.TeamLock.Enable (default 1, requires CFBG.Battlefield.Enable = 1). When disabled, every join re-balances exactly as before.

Issues Addressed

Players being reassigned to a different team after leaving and rejoining a Wintergrasp war.

Tests Performed

C++ codestyle (apps/codestyle/codestyle-cpp.py) passes. Not yet runtime-tested in-game.

How to Test the Changes

1. Enable CFBG.Enable, CFBG.Battlefield.Enable, and CFBG.Battlefield.TeamLock.Enable.
2. Join a Wintergrasp war and note the assigned faction.
3. Leave the war (and/or the zone, and/or relog) and rejoin the same war — the assigned faction should be unchanged.
4. After the war ends, a new war should balance assignments freshly.