Update DocumentApi for backend activate/deactivate response change

Backend now returns Document directly instead of wrapped
DocumentActionResponse. Remove unused DocumentActionResponse class.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

composeApp/src/commonMain/kotlin/com/tt/honeyDue/models/Document.kt

@@ -27,12 +27,6 @@ data class DocumentImage(
     @SerialName("uploaded_at") val uploadedAt: String? = null
 )
 
-@Serializable
-data class DocumentActionResponse(
-    val message: String,
-    val document: Document
-)
-
 @Serializable
 data class Document(
     val id: Int? = null,