test: DictionaryRepositoryImplTest 补 appCtx 注入

上游 #1855 合入起即在 JVM 环境挂（appCtx 未初始化），CI 不跑测试
所以无人发现。按 AboutViewModelTest 惯用法在 @Before 注入。

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/src/test/java/io/legado/app/data/repository/DictionaryRepositoryImplTest.kt

@@ -9,7 +9,9 @@ import org.junit.Before
 import org.junit.Test
 import org.junit.runner.RunWith
 import org.robolectric.RobolectricTestRunner
+import org.robolectric.RuntimeEnvironment
 import org.robolectric.annotation.Config
+import splitties.init.injectAsAppCtx
 import java.util.UUID
 import java.util.concurrent.CountDownLatch
 import java.util.concurrent.Executors
@@ -23,6 +25,7 @@ class DictionaryRepositoryImplTest {
 
     @Before
     fun setUp() {
+        RuntimeEnvironment.getApplication().injectAsAppCtx()
         repository = DictionaryRepositoryImpl()
         book = Book(
             bookUrl = "dictionary-test-${UUID.randomUUID()}",