refactor: convert Komga config to Server Action

- Add src/app/actions/config.ts with saveKomgaConfig
- Update KomgaSettings to use Server Action
- Remove POST from api/komga/config route (keep GET)

src/app/actions/config.ts

@@ -0,0 +1,45 @@
+"use server";
+
+import { revalidatePath } from "next/cache";
+import { ConfigDBService } from "@/lib/services/config-db.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { AppError } from "@/utils/errors";
+import type { KomgaConfig, KomgaConfigData } from "@/types/komga";
+
+interface SaveConfigInput {
+  url: string;
+  username: string;
+  password?: string;
+  authHeader?: string;
+}
+
+/**
+ * Sauvegarde la configuration Komga
+ */
+export async function saveKomgaConfig(
+  config: SaveConfigInput
+): Promise<{ success: boolean; message: string; data?: KomgaConfig }> {
+  try {
+    const configData: KomgaConfigData = {
+      url: config.url,
+      username: config.username,
+      password: config.password,
+      authHeader: config.authHeader || "",
+    };
+    const mongoConfig = await ConfigDBService.saveConfig(configData);
+
+    // Invalider le cache
+    revalidatePath("/settings");
+
+    return {
+      success: true,
+      message: "Configuration sauvegardée",
+      data: mongoConfig,
+    };
+  } catch (error) {
+    if (error instanceof AppError) {
+      return { success: false, message: error.message };
+    }
+    return { success: false, message: "Erreur lors de la sauvegarde" };
+  }
+}