Implement corpse reclaim: store death position and show Resurrect button

When a player releases spirit, the server sends SMSG_DEATH_RELEASE_LOC
with the corpse map and position. Store this so the ghost can reclaim.

New flow:
- SMSG_DEATH_RELEASE_LOC now stores corpseMapId_/corpseX_/Y_/Z_ instead
  of logging and discarding
- canReclaimCorpse(): true when ghost is on same map within 40 yards of
  stored corpse position
- reclaimCorpse(): sends CMSG_RECLAIM_CORPSE (no payload)
- renderReclaimCorpseButton(): shows "Resurrect from Corpse" button at
  bottom-center when canReclaimCorpse() is true

include/ui/game_screen.hpp

@@ -228,6 +228,7 @@ private:
     void renderTrainerWindow(game::GameHandler& gameHandler);
     void renderTaxiWindow(game::GameHandler& gameHandler);
     void renderDeathScreen(game::GameHandler& gameHandler);
+    void renderReclaimCorpseButton(game::GameHandler& gameHandler);
     void renderResurrectDialog(game::GameHandler& gameHandler);
     void renderEscapeMenu();
     void renderSettingsWindow();