Backward swimming was using 50% of forward swim speed as a hardcoded
fallback. Wire up the server-authoritative swim back speed so Warlock
Dark Pact, buffs, and server-forced speed changes all apply correctly
when swimming backward.
- game_handler.hpp: add getServerSwimBackSpeed() accessor
- camera_controller.hpp: add swimBackSpeedOverride_ field + setter
- camera_controller.cpp: apply swimBackSpeedOverride_ when player
swims backward without forward input; fall back to 50% of swim speed
- application.cpp: sync swim back speed each frame
a33f635490