feat: localize all UI text to Korean

Translate all user-facing strings to Korean across 25 files:
- UI screens: title, nickname, lobby, class select, waiting, game,
  shop, result, help, leaderboard, achievements, codex, stats
- Game logic: combat logs, events, achievements, mutations, emotes,
  lobby errors, session messages
- Keep English for: class names, monster names, item names, relic names

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

entity/player.go

@@ -179,22 +179,22 @@ func (p *Player) TickEffects() []string {
 			if p.HP <= 0 {
 				p.HP = 1 // Poison can't kill, leaves at 1 HP
 			}
-			msgs = append(msgs, fmt.Sprintf("%s takes %d poison damage", p.Name, e.Value))
+			msgs = append(msgs, fmt.Sprintf("%s 독 피해 %d", p.Name, e.Value))
 		case StatusBurn:
 			p.HP -= e.Value
 			if p.HP <= 0 {
 				p.HP = 0
 				p.Dead = true
 			}
-			msgs = append(msgs, fmt.Sprintf("%s takes %d burn damage", p.Name, e.Value))
+			msgs = append(msgs, fmt.Sprintf("%s 화상 피해 %d", p.Name, e.Value))
 		case StatusFreeze:
-			msgs = append(msgs, fmt.Sprintf("%s is frozen!", p.Name))
+			msgs = append(msgs, fmt.Sprintf("%s 동결됨!", p.Name))
 		case StatusBleed:
 			p.HP -= e.Value
-			msgs = append(msgs, fmt.Sprintf("%s takes %d bleed damage", p.Name, e.Value))
+			msgs = append(msgs, fmt.Sprintf("%s 출혈 피해 %d", p.Name, e.Value))
 			e.Value++ // Bleed intensifies each turn
 		case StatusCurse:
-			msgs = append(msgs, fmt.Sprintf("%s is cursed! Healing reduced", p.Name))
+			msgs = append(msgs, fmt.Sprintf("%s 저주 상태! 회복량 감소", p.Name))
 		}
 		if p.HP < 0 {
 			p.HP = 0

entity/player_test.go

@@ -200,7 +200,7 @@ func TestBleedEffect(t *testing.T) {
 	p.AddEffect(ActiveEffect{Type: StatusBleed, Duration: 3, Value: 2})
 
 	msgs := p.TickEffects()
-	if len(msgs) == 0 || !strings.Contains(msgs[0], "bleed") {
+	if len(msgs) == 0 || !strings.Contains(msgs[0], "출혈") {
 		t.Error("expected bleed damage message")
 	}
 	if p.HP != startHP-2 {
@@ -231,7 +231,7 @@ func TestFreezeTickMessage(t *testing.T) {
 	p := NewPlayer("Test", ClassMage)
 	p.AddEffect(ActiveEffect{Type: StatusFreeze, Duration: 1, Value: 0})
 	msgs := p.TickEffects()
-	if len(msgs) == 0 || !strings.Contains(msgs[0], "frozen") {
+	if len(msgs) == 0 || !strings.Contains(msgs[0], "동결") {
 		t.Error("expected freeze message")
 	}
 	// Freeze duration 1 -> removed after tick