refactor: convert library scan to Server Action

- Add src/app/actions/library.ts with scanLibrary
- Update ScanButton to use Server Action
- Remove POST from api/komga/libraries/[libraryId]/scan route

src/app/actions/library.ts

@@ -0,0 +1,28 @@
+"use server";
+
+import { revalidatePath } from "next/cache";
+import { LibraryService } from "@/lib/services/library.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { AppError } from "@/utils/errors";
+
+/**
+ * Lance un scan de bibliothèque
+ */
+export async function scanLibrary(
+  libraryId: string
+): Promise<{ success: boolean; message: string }> {
+  try {
+    await LibraryService.scanLibrary(libraryId, false);
+
+    // Invalider le cache de la bibliothèque
+    revalidatePath(`/libraries/${libraryId}`);
+    revalidatePath("/libraries");
+
+    return { success: true, message: "Scan lancé" };
+  } catch (error) {
+    if (error instanceof AppError) {
+      return { success: false, message: error.message };
+    }
+    return { success: false, message: "Erreur lors du scan" };
+  }
+}