feat: mail phase 2 - delete, move, drafts

- Add deleted_at field to Mail/MailAccount/MailFolder models
- Add DELETE /{mail_id} endpoint (soft-delete + IMAP EXPUNGE)
- Add POST /{mail_id}/move endpoint (IMAP UID MOVE + folder_id update)
- Add POST /drafts and PUT /drafts/{id} endpoints (save/edit drafts)
- Add imap_delete_mail() and imap_move_mail() service functions
- Add save_draft() and update_draft() service functions
- Frontend: deleteMail, moveMail, saveDraft, updateDraft API functions
- ComposeModal: draft mode with Save Draft button
- MailDetail: delete/move buttons, edit-draft for drafts
- Mail.tsx: bulk delete/move, move dropdown, draft handlers
- i18n: 13 new keys (de/en)

frontend/src/components/mail/MailDetail.tsx

@@ -19,6 +19,9 @@ export interface MailDetailProps {
   onToggleFlag: (mail: Mail) => void;
   onDownloadAttachment: (mailId: string, attachment: MailAttachment) => void;
   downloadingAttachmentId: string | null;
+  onDelete?: (mail: Mail) => void;
+  onMove?: (mail: Mail) => void;
+  onEditDraft?: (mail: Mail) => void;
 }
 
 function formatFullDate(dateStr: string): string {
@@ -47,6 +50,9 @@ export function MailDetail({
   onToggleFlag,
   onDownloadAttachment,
   downloadingAttachmentId,
+  onDelete,
+  onMove,
+  onEditDraft,
 }: MailDetailProps) {
   const { t } = useTranslation();
 
@@ -98,20 +104,32 @@ export function MailDetail({
     <div className="flex flex-col h-full" data-testid="mail-detail">
       {/* Toolbar */}
       <div className="flex items-center gap-1 sm:gap-2 px-3 py-2 md:px-4 md:py-3 border-b border-secondary-200 overflow-x-auto" data-testid="mail-detail-toolbar">
-        <Button variant="secondary" size="sm" onClick={() => onReply(mail)} icon={
-          <svg className="w-4 h-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" aria-hidden="true">
-            <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M3 10h10a8 8 0 018 8v2M3 10l6 6m-6-6l6-6" />
-          </svg>
-        }>
-          {t('mail.reply')}
-        </Button>
-        <Button variant="secondary" size="sm" onClick={() => onForward(mail)} icon={
-          <svg className="w-4 h-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" aria-hidden="true">
-            <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M21 10H11a8 8 0 00-8 8v2m18-10l-6-6m6 6l-6 6" />
-          </svg>
-        }>
-          {t('mail.forward')}
-        </Button>
+        {mail.is_draft && onEditDraft ? (
+          <Button variant="secondary" size="sm" onClick={() => onEditDraft(mail)} icon={
+            <svg className="w-4 h-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" aria-hidden="true">
+              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M11 5H6a2 2 0 00-2 2v11a2 2 0 002 2h11a2 2 0 002-2v-5m-1.414-9.414a2 2 0 112.828 2.828L11.828 15H9v-2.828l8.586-8.586z" />
+            </svg>
+          }>
+            {t('mail.editDraft')}
+          </Button>
+        ) : (
+          <>
+            <Button variant="secondary" size="sm" onClick={() => onReply(mail)} icon={
+              <svg className="w-4 h-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" aria-hidden="true">
+                <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M3 10h10a8 8 0 018 8v2M3 10l6 6m-6-6l6-6" />
+              </svg>
+            }>
+              {t('mail.reply')}
+            </Button>
+            <Button variant="secondary" size="sm" onClick={() => onForward(mail)} icon={
+              <svg className="w-4 h-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" aria-hidden="true">
+                <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M21 10H11a8 8 0 00-8 8v2m18-10l-6 6m6-6l-6-6" />
+              </svg>
+            }>
+              {t('mail.forward')}
+            </Button>
+          </>
+        )}
         <Button
           variant="ghost"
           size="sm"
@@ -125,6 +143,20 @@ export function MailDetail({
         >
           {mail.is_flagged ? t('mail.unflag') : t('mail.flag')}
         </Button>
+        {onMove && (
+          <Button
+            variant="ghost"
+            size="sm"
+            onClick={() => onMove(mail)}
+            icon={
+              <svg className="w-4 h-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" aria-hidden="true">
+                <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M17 8l4 4m0 0l-4 4m4-4H3" />
+              </svg>
+            }
+          >
+            {t('mail.move')}
+          </Button>
+        )}
         <div className="flex-1" />
         <Button
           variant="ghost"
@@ -138,6 +170,20 @@ export function MailDetail({
         >
           {t('mail.createEvent')}
         </Button>
+        {onDelete && (
+          <Button
+            variant="ghost"
+            size="sm"
+            onClick={() => onDelete(mail)}
+            icon={
+              <svg className="w-4 h-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" aria-hidden="true">
+                <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M19 7l-.867 12.142A2 2 0 0116.138 21H7.862a2 2 0 01-1.995-1.858L5 7m5 4v6m4-6v6m1-10V4a1 1 0 00-1-1h-4a1 1 0 00-1 1v3M4 7h16" />
+              </svg>
+            }
+          >
+            {t('mail.delete')}
+          </Button>
+        )}
       </div>
 
       {/* Headers */}