feat: enhance accessibility and testing with data-test attributes and improve error handling

apps/web/i18n/messages/en/newsletter.json

@@ -0,0 +1,76 @@
+{
+  "nav": {
+    "newsletters": "Newsletters",
+    "templates": "Templates",
+    "newNewsletter": "New Newsletter"
+  },
+  "list": {
+    "title": "Newsletters",
+    "subtitle": "Create and send newsletters",
+    "newNewsletter": "New Newsletter",
+    "noNewsletters": "No newsletters found",
+    "createFirst": "Create your first newsletter to get started.",
+    "subject": "Subject",
+    "noSubject": "(No Subject)",
+    "recipients": "Recipients",
+    "created": "Created",
+    "sent": "Sent",
+    "totalSent": "Sent",
+    "totalRecipients": "Total Recipients"
+  },
+  "detail": {
+    "title": "Newsletter Details",
+    "backToList": "Back to Newsletters",
+    "sendNewsletter": "Send Newsletter",
+    "recipientsSection": "Recipients",
+    "sentCount": "Sent",
+    "failedCount": "Failed",
+    "noRecipients": "No recipients added. Add recipients from your member list.",
+    "recipientName": "Name",
+    "recipientEmail": "Email",
+    "recipientStatus": "Status",
+    "notFound": "Newsletter not found"
+  },
+  "form": {
+    "content": "Newsletter Content",
+    "subject": "Subject *",
+    "bodyHtml": "Content (HTML) *",
+    "bodyHtmlPlaceholder": "<h1>Hello!</h1><p>Your newsletter content...</p>",
+    "bodyText": "Plain Text Version",
+    "bodyTextHelp": "Plain text fallback for email clients without HTML support",
+    "schedule": "Schedule",
+    "scheduledDate": "Scheduled Send (optional)",
+    "scheduleHelp": "Leave empty to save the newsletter as a draft.",
+    "created": "Newsletter created successfully",
+    "errorCreating": "Error creating newsletter"
+  },
+  "templates": {
+    "title": "Newsletter Templates",
+    "subtitle": "Reusable templates for newsletters",
+    "newTemplate": "New Template",
+    "noTemplates": "No templates found",
+    "createFirst": "Create your first newsletter template for reuse in campaigns.",
+    "allTemplates": "All Templates ({count})",
+    "name": "Name",
+    "subject": "Subject",
+    "variables": "Variables"
+  },
+  "status": {
+    "draft": "Draft",
+    "scheduled": "Scheduled",
+    "sending": "Sending",
+    "sent": "Sent",
+    "failed": "Failed"
+  },
+  "recipientStatus": {
+    "pending": "Pending",
+    "sent": "Sent",
+    "failed": "Failed",
+    "bounced": "Bounced"
+  },
+  "common": {
+    "cancel": "Cancel",
+    "creating": "Creating...",
+    "create": "Create Newsletter"
+  }
+}