fix(db): correct the UTC skew and retire the stale outbox backlog

packages/db/prisma/migrations/20260818011000_notification_backlog_retire/migration.sql

@@ -0,0 +1,38 @@
+-- Two corrections to 20260818003000_notification_retry_bounds.
+--
+-- 1. UTC skew. That migration backfilled next_attempt_at with CURRENT_TIMESTAMP,
+--    which returns the session's *local* time. The database runs Europe/Berlin
+--    while Prisma stores and reads these columns as UTC, so every existing row
+--    landed two hours in the future and the poller stopped selecting them
+--    entirely. Confirmed on production: TimeZone Europe/Berlin, next_attempt_at
+--    00:18:40 local for a migration that ran at 22:18 UTC.
+--
+--    Rule for next time: a backfill of a Prisma DateTime uses
+--    now() AT TIME ZONE 'utc', never CURRENT_TIMESTAMP or now().
+--
+--    The column DEFAULT is deliberately left alone. CURRENT_TIMESTAMP is what
+--    Prisma emits for @default(now()), so changing it would show up as schema
+--    drift on the next migrate dev, and Prisma supplies the value on every
+--    insert anyway — the default is never reached in practice.
+--
+-- 2. The stale backlog. The retry bounds arrived to find 19 undeliverable
+--    applicant DMs queued since 2026-07-03 (12 message, 7 status_change)
+--    against a batch size of 25, so the outbox was six rows short of starving
+--    every newer notification.
+--
+--    Simply making them due would have delivered six-week-old status
+--    notifications to applicants who have long since moved on. Retire anything
+--    older than a week unsent instead: the status page carries the current
+--    state at any time, and a very late nudge is worse than none. Expressed as
+--    an age rule rather than a list of ids so it reads as the policy it is.
+UPDATE "notifications"
+   SET "read_at"    = now() AT TIME ZONE 'utc',
+       "last_error" = 'retired: stale outbox row (predates retry bounds)'
+ WHERE "read_at" IS NULL
+   AND "created_at" < (now() AT TIME ZONE 'utc') - interval '7 days';
+
+-- Whatever is recent enough to still be worth sending becomes due immediately,
+-- in the same UTC frame Prisma reads.
+UPDATE "notifications"
+   SET "next_attempt_at" = "created_at"
+ WHERE "read_at" IS NULL;