feat(deeplink): merge and display config in import dialog

Enhance import dialog to fetch and display complete config.
- Call mergeDeeplinkConfig API when config is present
- Add UTF-8 base64 decoding support for config content
- Add scrollable content area with custom scrollbar styling
- Show complete configuration before user confirms import

src/lib/api/deeplink.ts

@@ -30,6 +30,18 @@ export const deeplinkApi = {
     return invoke("parse_deeplink", { url });
   },
 
+  /**
+   * Merge configuration from Base64/URL into a deep link request
+   * This is used to show the complete configuration in the confirmation dialog
+   * @param request The deep link import request
+   * @returns Merged deep link request with config fields populated
+   */
+  mergeDeeplinkConfig: async (
+    request: DeepLinkImportRequest,
+  ): Promise<DeepLinkImportRequest> => {
+    return invoke("merge_deeplink_config", { request });
+  },
+
   /**
    * Import a provider from a deep link request
    * @param request The deep link import request