fix(image): Coil 2 대응 BlurTransformation 구현을 추가한다

app/src/test/java/kr/co/vividnext/sodalive/common/image/BlurTransformationTest.kt

@@ -0,0 +1,35 @@
+package kr.co.vividnext.sodalive.common.image
+
+import android.content.Context
+import io.mockk.mockk
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertThrows
+import org.junit.Test
+
+class BlurTransformationTest {
+
+    @Test
+    fun `cacheKey includes radius and sampling`() {
+        val transformation = BlurTransformation(
+            context = mockk<Context>(relaxed = true),
+            radius = 25f,
+            sampling = 2.5f
+        )
+
+        assertEquals(
+            "kr.co.vividnext.sodalive.common.image.BlurTransformation-25.0-2.5",
+            transformation.cacheKey
+        )
+    }
+
+    @Test
+    fun `constructor rejects radius above max`() {
+        assertThrows(IllegalArgumentException::class.java) {
+            BlurTransformation(
+                context = mockk<Context>(relaxed = true),
+                radius = 26f,
+                sampling = 2.5f
+            )
+        }
+    }
+}