feat: refactor MailViewer and add utility functions for email handling and attachment processing

frontend/src/lib/utils/mail/index.ts

@@ -0,0 +1,37 @@
+/**
+ * Mail utilities barrel export
+ */
+
+// Constants
+export {
+  IFRAME_UTIL_HTML,
+  EMAIL_EXTENSIONS,
+  CONTENT_TYPES,
+  PEC_FILES,
+} from './constants';
+
+// Data utilities
+export {
+  arrayBufferToBase64,
+  createDataUrl,
+  looksLikeBase64,
+  tryDecodeBase64,
+} from './data-utils';
+
+// Attachment handlers
+export {
+  openPDFAttachment,
+  openImageAttachment,
+  openEMLAttachment,
+  type AttachmentHandlerResult,
+} from './attachment-handlers';
+
+// Email loader
+export {
+  getEmailFileType,
+  isEmailFile,
+  loadEmailFromPath,
+  openAndLoadEmail,
+  processEmailBody,
+  type LoadEmailResult,
+} from './email-loader';