feat(tasks): snooze — park a task at the bottom until a time

Snooze puts a task out of the way without finishing it or filing it: it sinks to
the bottom of its list and greys, and comes back on its own when its time passes.
No job wakes it — "snoozed" is just snoozed_until being still in the future, read
against the clock each time the list is ordered.

- `snoozed_until` on tasks (migration 0031); the list order sinks a still-snoozed
  task below everything, and it rejoins its place the moment the time passes.
- POST /tasks/{id}/snooze {until} — an RFC3339 time to snooze to, or empty to wake.
  Nothing else about the task moves; a snooze is about when you want to see it, not
  when it is due.
- The task drawer gains quick picks (this evening / tomorrow / next week) and a
  custom time, and a Wake now once it is snoozed. The row dims and carries a
  "snoozed until X" mark, and the list keeps snoozed tasks at the foot — the client
  sorts the same way the server does, so a drag-sorted list does not jump on reload.

Tests: snooze sinks a task below one made after it and waking returns it (Go); and
from the drawer the row greys, shows the mark, and un-greys on wake (e2e). Full
suites green.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

web/src/lib/stores.svelte.js

@@ -408,6 +408,19 @@ class AppState {
 	 * and time are left alone, so making a task longer on the calendar does not
 	 * also reschedule it.
 	 */
+	/**
+	 * Snoozes a task until an ISO time, or wakes it when `until` is empty. Nothing
+	 * else about the task moves — a snooze is about when you want to see it, not when
+	 * it is due. Optimistic, so it greys and sinks at once.
+	 */
+	async snooze(id, until) {
+		await this.#optimistic(
+			id,
+			{ snoozed_until: until || undefined },
+			() => api.snoozeTask(id, until || '')
+		);
+	}
+
 	async resize(id, minutes) {
 		const previous = this.get(id);
 		if (!previous) return;