feat(i18n): migrate hardcoded German strings to t() across 104 components/pages — AST-based batch with re-parse gate, 423 new de.json keys; tsc clean; vitest failures byte-identical to clean-tree baseline (pre-existing)

frontend/src/components/mail/MailComposeForm.tsx

@@ -304,7 +304,7 @@ export function MailComposeForm({
           label={t('mail.to')}
           {...register('to')}
           error={errorMsg(errors.to?.message)}
-          placeholder="recipient@example.com"
+          placeholder={t('mailComposeForm.recipientexamplecom')}
           required
           data-testid="compose-to"
         />
@@ -323,13 +323,13 @@ export function MailComposeForm({
                 label={t('mail.cc')}
                 {...register('cc')}
                 error={errorMsg(errors.cc?.message)}
-                placeholder="cc@example.com"
+                placeholder={t('mailComposeForm.ccexamplecom')}
               />
               <Input
                 label={t('mail.bcc')}
                 {...register('bcc')}
                 error={errorMsg(errors.bcc?.message)}
-                placeholder="bcc@example.com"
+                placeholder={t('mailComposeForm.bccexamplecom')}
               />
             </div>
           )}
@@ -377,7 +377,7 @@ export function MailComposeForm({
           >
             {t('mail.addAttachment')}
           </Button>
-          <span className="text-xs text-secondary-400">Max 25 MB per file</span>
+          <span className="text-xs text-secondary-400">{t('mailComposeForm.max25mbperfile')}</span>
         </div>
         {attachments.length > 0 && (
           <ul className="mt-2 space-y-1">