wallet: lock the ingest, pair on time and app, skip notices, ECB fallback

Four defects found reviewing a month of overseas wallet rows:

- Race: n8n posts a poll's items concurrently and both halves of a tap
  usually share a poll, so each ran findPairedRow before the other inserted.
  11 taps became 22 rows (A$3,841.40), identical created_at on every pair.
  One advisory lock now covers re-check -> pair -> adopt -> insert, on the
  transaction's own connection (a second pooled one per request deadlocks a
  burst). Mutation-tested: without the lock the concurrent test fails 3/3.
- Pair window: amount within +/-1 DAY folded the UNICEF $50 donation and an
  unrelated $50 Amex charge 17h later into one row and renamed it. A pair is
  now minutes apart AND from two different apps. Needs when/where a
  notification arrived: migration 0039 adds expense_metadata.notified_at /
  notif_app, backfilled from capture.wallet_events (144 rows). A merged half
  now records wallet_evt:<id>, so a replay cannot merge it twice.
- Not purchases: a CommBank overdraft notice became a $21.21 purchase named
  "To avoid fees and interest," (the Westpac fixed-width parser ran on a
  CommBank body). Account notices and transit-card balance drawdowns are
  skipped; the descriptor parser only runs on Westpac.
- FX: with no ledger history (Hong Kong) every tap stored A$0.00. The ECB
  rate via Frankfurter is the fallback, flagged rate_ecb; the ledger median
  stays first because it carries the card's FX fee.

Also: dates in Australia/Melbourne like the statements (UTC slicing filed 28
of 134 rows a day early), and test:setup now actually rebuilds personal_test
-- replaying the dump over it never applied a migration.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

prisma/schema.prisma

@@ -237,6 +237,9 @@ model expense_metadata {
   tender_raw             String?
   receipt_sha256         String?
   receipt_group          String?
+  // 0039 — when/where a wallet notification arrived; the pair merge needs both.
+  notified_at            DateTime?    @db.Timestamptz(6)
+  notif_app              String?
   transaction           transactions? @relation(fields: [transaction_id], references: [id], onDelete: Cascade)
 
   @@unique([source, order_reference], name: "uq_expense_source_order")