feat: 테마 자체의 정보만 담고 있는 별도의 도메인 추가

src/main/kotlin/roomescape/theme/business/domain/ThemeInfo.kt

@@ -0,0 +1,15 @@
+package roomescape.theme.business.domain
+
+class ThemeInfo(
+    val id: Long,
+    val name: String,
+    val description: String,
+    val difficulty: String,
+    val thumbnailUrl: String,
+    val price: Int,
+    val minParticipants: Short,
+    val maxParticipants: Short,
+    val availableMinutes: Short,
+    val expectedMinutesFrom: Short,
+    val expectedMinutesTo: Short
+)