Implement SMSG_SPELLDAMAGESHIELD, SMSG_SPELLORDAMAGE_IMMUNE; route MSG_MOVE in SMSG_MULTIPLE_MOVES

- SMSG_SPELLDAMAGESHIELD: parse victim/caster/damage fields and show SPELL_DAMAGE
  combat text for player-relevant events (damage shields like Thorns)
- SMSG_SPELLORDAMAGE_IMMUNE: parse packed caster/victim guids and show new
  IMMUNE combat text type when player is involved in an immunity event
- Add CombatTextEntry::IMMUNE type to spell_defines.hpp and render it as
  white "Immune!" in the combat text overlay
- handleCompressedMoves: add MSG_MOVE_* routing so SMSG_MULTIPLE_MOVES
  sub-packets (player movement batches) are dispatched to handleOtherPlayerMovement
  instead of logged as unhandled; fix runtime-opcode lookup (non-static array)

src/ui/game_screen.cpp

@@ -4671,6 +4671,10 @@ void GameScreen::renderCombatText(game::GameHandler& gameHandler) {
                     snprintf(text, sizeof(text), "+%d XP", entry.amount);
                     color = ImVec4(0.7f, 0.3f, 1.0f, alpha);  // Purple for XP
                     break;
+                case game::CombatTextEntry::IMMUNE:
+                    snprintf(text, sizeof(text), "Immune!");
+                    color = ImVec4(0.9f, 0.9f, 0.9f, alpha);  // White for immune
+                    break;
                 default:
                     snprintf(text, sizeof(text), "%d", entry.amount);
                     color = ImVec4(1.0f, 1.0f, 1.0f, alpha);