feat: mail list font size, remove Termin toolbar, rename Flagge to Markierung with symbol picker

- Mail list: title and subject font text-xs -> text-sm
- Remove Termin (create-event) toolbar button
- Rename Flagge -> Markierung with select dropdown (star, flag, bookmark, important, question)
- Backend: add flag_type column to Mail model + migration 0006
- Backend: flag_type in MailFlagsUpdate schema, update_flags route, mail_to_response
- Frontend: flag_type in Mail interface, FlagUpdatePayload, MailList symbol display

frontend/src/pages/Mail.tsx

@@ -340,6 +340,21 @@ export function MailPage() {
     [toast],
   );
 
+  // Handle set flag type (symbol picker)
+  const handleSetFlagType = useCallback(
+    async (mail: Mail, flagType: string) => {
+      try {
+        const isFlagged = flagType !== '';
+        await updateFlags(mail.id, { is_flagged: isFlagged, flag_type: flagType || null });
+        setSelectedMail((prev) => (prev ? { ...prev, is_flagged: isFlagged, flag_type: flagType || null } : prev));
+        setMails((prev) => prev.map((m) => (m.id === mail.id ? { ...m, is_flagged: isFlagged, flag_type: flagType || null } : m)));
+      } catch (err) {
+        toast.error(err instanceof Error ? err.message : String(err));
+      }
+    },
+    [toast],
+  );
+
   // Handle toggle select for bulk operations
   const handleToggleSelect = useCallback((mailId: string) => {
     setSelectedMailIds((prev) => {
@@ -532,29 +547,21 @@ export function MailPage() {
       {
         id: 'flag',
         plugin: 'mail',
-        label: 'Flagge',
+        label: 'Markierung',
         group: 'mail-actions',
         disabled: !hasMail,
-        active: selectedMailFlagged,
-        icon: (
-          <svg className="w-3.5 h-3.5" fill="none" viewBox="0 0 24 24" stroke="currentColor">
-            <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M3 21v-4m0 0V5a2 2 0 012-2h6.5l1 1H21l-3 6 3 6h-8.5l-1-1H5a2 2 0 00-2 2zm9-13.5V9" />
-          </svg>
-        ),
-        onClick: () => selectedMail && handleToggleFlag(selectedMail),
-      },
-      {
-        id: 'create-event',
-        plugin: 'mail',
-        label: 'Termin',
-        group: 'mail-actions',
-        disabled: !hasMail,
-        icon: (
-          <svg className="w-3.5 h-3.5" fill="none" viewBox="0 0 24 24" stroke="currentColor">
-            <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M8 7V3m8 4V3m-9 8h10M5 21h14a2 2 0 002-2V7a2 2 0 00-2-2H5a2 2 0 00-2 2v12a2 2 0 002 2z" />
-          </svg>
-        ),
-        onClick: () => selectedMail && handleCreateEvent(selectedMail),
+        type: 'select' as const,
+        selectValue: selectedMail?.flag_type || '',
+        selectOptions: [
+          { value: '', label: 'Keine' },
+          { value: 'star', label: '⭐ Stern' },
+          { value: 'flag', label: '🚩 Flagge' },
+          { value: 'bookmark', label: '🔖 Lesezeichen' },
+          { value: 'important', label: '❗ Wichtig' },
+          { value: 'question', label: '❓ Frage' },
+        ],
+        onSelect: (value: string) => selectedMail && handleSetFlagType(selectedMail, value),
+        onClick: () => {},
       },
       {
         id: 'delete',
@@ -667,7 +674,7 @@ export function MailPage() {
     }
     registerItems('mail', items);
     return () => unregisterPlugin('mail');
-  }, [selectedMailId, selectedMailFlagged, selectedMailIds, handleSearch, handleCompose, handleReply, handleForward, handleToggleFlag, handleCreateEvent, handleDeleteMail, handleBulkDelete, handleBulkMarkRead, handleBulkMarkUnread, t]);
+  }, [selectedMailId, selectedMailFlagged, selectedMailIds, handleSearch, handleCompose, handleReply, handleForward, handleToggleFlag, handleSetFlagType, handleDeleteMail, handleBulkDelete, handleBulkMarkRead, handleBulkMarkUnread, t]);
 
   if (loadingAccounts) {
     return (