feat(character-gallery): 갤러리 탭 UI/페이징 및 API 연동, DI 적용

- API: CharacterApi에 이미지 리스트 API 추가(characterId, page, size)
- VM: 페이징(loadInitial/loadNext), 요청 중복 방지, 마지막 페이지 판단, 누적 리스트 관리
- UI: ProgressBar(배경 #37474F/진행 #3BB9F1, radius 999dp, 비활성) + 좌/우 텍스트 구성
- Grid 3열 + 2dp 간격, item 4:5 비율, 잠금/구매 버튼 UI 적용
- UX: tv_ratio_right에서 ownedCount만 #FDD453로 강조(white 대비)

app/src/main/res/layout/item_character_gallery.xml

@@ -0,0 +1,66 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content">
+
+    <!-- 이미지 컨테이너: 4:5 비율(800:1000) -->
+    <ImageView
+        android:id="@+id/iv_image"
+        android:layout_width="0dp"
+        android:layout_height="0dp"
+        android:contentDescription="@null"
+        android:scaleType="centerCrop"
+        app:layout_constraintDimensionRatio="4:5"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
+
+    <LinearLayout
+        android:id="@+id/ll_lock"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:gravity="center"
+        android:orientation="vertical"
+        android:visibility="gone"
+        app:layout_constraintBottom_toBottomOf="@id/iv_image"
+        app:layout_constraintEnd_toEndOf="@id/iv_image"
+        app:layout_constraintStart_toStartOf="@id/iv_image"
+        app:layout_constraintTop_toTopOf="@id/iv_image">
+
+        <ImageView
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:contentDescription="@null"
+            android:src="@drawable/ic_new_lock" />
+
+        <LinearLayout
+            android:id="@+id/btn_buy"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_margin="10dp"
+            android:background="@drawable/bg_buy_button"
+            android:gravity="center_vertical"
+            android:paddingHorizontal="10dp"
+            android:paddingVertical="3dp">
+
+            <ImageView
+                android:layout_width="16dp"
+                android:layout_height="16dp"
+                android:layout_marginEnd="4dp"
+                android:contentDescription="@null"
+                android:src="@drawable/ic_can" />
+
+            <TextView
+                android:id="@+id/tv_price"
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:fontFamily="@font/pretendard_bold"
+                android:textColor="#263238"
+                android:textSize="16sp"
+                tools:text="0" />
+        </LinearLayout>
+    </LinearLayout>
+
+</androidx.constraintlayout.widget.ConstraintLayout>