feat(tasks): repeating tasks (daily, weekly, monthly, yearly)

- recurrence on tasks, set in the detail dialog; 🔁 on rows and Kanban cards
- Completing a repeating task (detail, list, Kanban drag to done, note
  checkbox) creates the next one: title, tags, priority, notes, list,
  assignees and rule copied, subtasks reset, first open column, due date
  one interval later (month end clamped); pushed live as TASK_CREATED
- Each task spawns at most once (re-open + complete makes no duplicate)
- Export/import keep the rule (Obsidian Tasks "🔁 every week", JSON field)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/storage/import_markdown_test.go

@@ -41,6 +41,7 @@ func seedAnna(t *testing.T, store *Store, anna *domain.User) {
 	_, _ = store.UpdateThoughtTriage(anna.ID, task.ID, "keep", "task", "", "2026-11-02", tl.ID)
 	subs := []domain.SubTask{{ID: "s1", Title: "Leiter holen", IsCompleted: true}}
 	_, _ = store.UpdateThoughtDetails(anna.ID, task.ID, nil, nil, nil, nil, nil, nil, nil, &subs, nil)
+	_ = store.SetTaskRecurrence(anna.ID, task.ID, "monthly")
 	list, _ := store.CreateList(anna.ID, "Einkauf", "🛒", "shopping")
 	item, _ := store.CreateListItem(list.ID, "Milch", "Kühlregal", "2L", 0, anna.ID)
 	_, _ = store.ToggleListItem(item.ID, true, anna.ID, "Anna")
@@ -66,7 +67,7 @@ func checkRestored(t *testing.T, store *Store, ben *domain.User) {
 		t.Fatalf("task list not restored: %+v / %+v", lists, tasks)
 	}
 	tk := tasks[0]
-	if tk.Content != "Fenster putzen" || tk.Priority != "urgent" || tk.DueDate != "2026-11-02" || tk.Notes != "Leiter im Keller" ||
+	if tk.Content != "Fenster putzen" || tk.Priority != "urgent" || tk.DueDate != "2026-11-02" || tk.Notes != "Leiter im Keller" || tk.Recurrence != "monthly" ||
 		len(tk.Subtasks) != 1 || !tk.Subtasks[0].IsCompleted || tk.TaskListID != lists[0].ID {
 		t.Errorf("task not restored: %+v", tk)
 	}
@@ -218,4 +219,3 @@ func TestImportBackupZip(t *testing.T) {
 	}
 	checkRestored(t, store, ben)
 }
-