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>

docs/openapi.yaml

@@ -805,6 +805,28 @@ paths:
         "200": { $ref: "#/components/responses/Task" }
         "404": { $ref: "#/components/responses/NotFound" }
 
+  /api/v1/tasks/{taskID}/snooze:
+    parameters:
+      - { name: taskID, in: path, required: true, schema: { type: string } }
+    post:
+      tags: [tasks]
+      summary: Snooze a task until a time, or wake it.
+      description: |
+        Parks the task at the bottom of its list, greyed, until `until` passes —
+        nothing else about it moves. An empty `until` wakes it now.
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              type: object
+              properties:
+                until: { type: string, format: date-time, description: "RFC3339; empty to wake." }
+      responses:
+        "200": { $ref: "#/components/responses/Task" }
+        "404": { $ref: "#/components/responses/NotFound" }
+        "422": { $ref: "#/components/responses/Validation" }
+
   /api/v1/tasks/quick-add:
     post:
       tags: [tasks]