feat(tasks): a task can repeat every N days from a dated start

A third period, { unit: "cycle", days, from }, cut in day-key space like
weeks and months, so each game's per-server reset carries over. Tasks on
it are tallied and switched apart (showCycleTasks, on by default), show
the days left in their chip, and the lower row's heading now names the
periods it holds.

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

src/client/components/TaskForm.tsx

@@ -122,7 +122,7 @@ export function TaskForm({
   const [f, setF] = useState<TaskFields>(() => ({
     game: initial?.game ?? lanes[0] ?? "",
     title: initial?.title ?? "",
-    unit: initial?.period.unit ?? "week",
+    unit: initial?.period.unit === "month" ? "month" : "week",
     weekday: initial?.period.unit === "week" ? initial.period.startsOn : 1,
     monthDay: String(initial?.period.unit === "month" ? initial.period.startsOn : 1),
     kind: initial?.measure.kind ?? "days",