feat: add opt-in daily Discord reminders with quiet hours

README.md

@@ -3,6 +3,8 @@
 Bun + Hono habit-tracking REST API with Drizzle ORM and local SQLite. The React Router
 client includes a homepage for signed-out visitors and a personal habit dashboard.
 
+See [deployment operations](docs/OPERATIONS.md) for backup, recovery, and monitoring.
+
 See [the REST API reference](docs/API.md) for habits, task recurrence, dated progress,
 combined calendars, historical corrections, daily resets, and optional count carryover.
 
@@ -345,3 +347,30 @@ existing delivery does not consume quota. Rejected attempts consume quota too;
 (comma-separated Discord IDs) restricts posting to community members you approve.
 An empty list permits all signed-in accounts. Restricted users can still preview
 and download PNGs. Quota rows expire and are pruned after 24 hours.
+
+### Daily reminders
+
+Open **Settings → Daily reminders** to opt into one private Discord DM when habits
+remain unfinished. Choose a local time and quiet hours; times follow the account
+timezone. Quiet-hour start is inclusive, end is exclusive, and equal times disable
+quiet hours. If the scheduled time falls in quiet hours, delivery waits until they
+end that same local day. A reminder missed for the whole day is not carried forward.
+
+The production server checks once a minute. `DISCORD_BOT_TOKEN` enables delivery;
+a sharing channel is not required for reminders. Users must be reachable by the
+bot (normally a shared Discord server and enabled DMs). A message contains only
+the unfinished-habit count and app link. Settings show the most recent delivery
+result, including blocked DMs or unconfirmed delivery. Uncheck the option and save
+to opt out. No reminders are enabled by default.
+
+`GET /api/reminders` returns settings and last delivery status. `PUT /api/reminders`
+requires authentication, matching Origin, and `{enabled, time, quietStart, quietEnd}`
+with `HH:MM` times. Per-user/date reservations persist across restarts and concurrent
+workers. Discord 429 retry deadlines are persisted; ambiguous message sends are
+not retried that day. Delivery records expire after 90 days. Restore disables
+reminders in the recovered database until users opt in again.
+
+The disposable `SHARE_PREVIEW=1 bun scripts/dashboard-preview.ts` mode also runs a
+reminder worker against a local transport stub. Set a reminder to `14:00` (its fixed
+Europe/Belgrade time), leave a habit unfinished, and inspect delivery status in
+settings or `/__preview/reminder`. No real Discord messages are sent in this mode.