fix: L1/L2 캐시 maxSize 상향 + AisTarget hitRate 타입 수정

- L1(5분): 700K→1.5M (실측 612K, 87% 포화 → 41%)
- L2(시간): 1.4M→3.5M (실측 1.27M, 91% 포화 → 36%)
- AisTarget hitRate: String("64.41%") → double(64.41)
  프론트엔드 .toFixed() 호출 시 타입 에러 수정

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/main/java/gc/mda/signal_batch/batch/reader/AisTargetCacheManager.java

@@ -221,9 +221,9 @@ public class AisTargetCacheManager {
         result.put("ttlMinutes", ttlMinutes);
         result.put("hitCount", stats.hitCount());
         result.put("missCount", stats.missCount());
-        result.put("hitRate", String.format("%.2f%%", stats.hitRate() * 100));
+        result.put("hitRate", stats.hitRate() * 100);
         result.put("evictionCount", stats.evictionCount());
-        result.put("utilizationPercent", String.format("%.2f%%", (cache.estimatedSize() * 100.0 / maxSize)));
+        result.put("utilizationPercent", cache.estimatedSize() * 100.0 / maxSize);
 
         return result;
     }

src/main/resources/application-prod.yml

@@ -278,11 +278,11 @@ app:
 
     five-min-track:
       ttl-minutes: 75
-      max-size: 700000       # 500K→700K (실측 504K, 30% 여유)
+      max-size: 1500000      # 700K→1.5M (실측 612K, 2.5배 여유)
 
     hourly-track:
       ttl-hours: 26
-      max-size: 1400000      # 780K→1.4M (실측 1.08M, 30% 여유, +1.5GB)
+      max-size: 3500000      # 1.4M→3.5M (실측 1.27M, 2.8배 여유)
 
 # 일일 항적 데이터 인메모리 캐시
 cache: