feat(bank): expose bank-reported balance (booked + available) in UI, reconciliation, MCP and v1 API (#2118)

* feat(bank): expose bank-reported balance (booked + available) in UI, reconciliation, MCP and v1 API

The PSD2 sync has fetched the bank's reported balance for years but the
data was stranded (F7): the Bank-page source picker read a cash_accounts
column no sync ever updated (frozen at connect time), reconciliation
hard-coded external_balance to null for bank accounts, and neither MCP
nor the v1 API exposed any balance at all, so the only path to a current
bank balance was logging into the bank.

- getAccountBalance now returns booked + available from the same
  quota-limited BALANCES response (previously all but one type discarded)
- every sync (manual + cron) mirrors balance, available_balance and
  balance_updated_at into cash_accounts, fixing the stale picker
- new cash_accounts.available_balance column (additive migration)
- reconciliation bank kind: external_balance = bank-reported balance,
  plus bank_reported_* fields and fetch timestamp in the bank block;
  difference math stays movement-based and untouched
- reconciliation view shows "Saldo enligt banken ... hamtat {date}"
- MCP gnubok_list_cash_accounts returns the three balance fields; the
  cash_today prompt now reports the bank's figure instead of teaching
  agents to answer with the bookkept 19xx balance
- new GET /api/v1/companies/{companyId}/cash-accounts endpoint

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ewu46quXgh9LSr9UwYusxm

* fix(bank): keep external_balance null for bank sign-offs; never fabricate a zero balance; guard the mirror against stale writers

Post-review fixes from the skeptic pass + CodeRabbit on PR #2118:

- external_balance stays null for the bank reconciliation kind: sign-off
  persists it into account_reconciliations and bokslutsbilagor computes
  closing - external from that row, so a today-balance stored on a
  balansdag sign-off printed a phantom warning-red differens in the
  year-end appendix. The bank-reported figure lives only in the
  timestamped bank_reported_* pair in the bank block, and only when its
  fetch timestamp exists (a balance of unknown age is suppressed).
- AccountOverview no longer falls back to today's date when the balance
  timestamp is missing; the line is omitted instead.
- getAccountBalance returns null on an empty BALANCES response instead
  of fabricating amount 0 with a fresh timestamp; sync keeps the
  previous stored value.
- updateBalancesFromSync only writes over an older-or-missing
  balance_updated_at, so an older sync run finishing later cannot move
  the mirrored balance backwards.
- The inline initial backfill (picker save) now mirrors fetched
  balances into cash_accounts too (accounts_data is deliberately not
  re-written there).
- cash_today MCP prompt mentions the gnubok_call_tool bridge for hosts
  that only see the default catalog.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ewu46quXgh9LSr9UwYusxm

* fix(bank): express the stale-writer guard as two literal predicates for the schema guard

The .or() with a template literal pushed the no-phantom-columns
unresolvable-expression count over its ceiling. Same semantics, two
updates: one for rows with an older timestamp, one for rows with none.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ewu46quXgh9LSr9UwYusxm

* fix(bank): rank interimBooked (ITBD) as a booked balance type before the generic fallback

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ewu46quXgh9LSr9UwYusxm

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

app/api/extensions/enable-banking/sync/cron/__tests__/route.test.ts

@@ -54,6 +54,15 @@ vi.mock('@/lib/reconciliation/bank-reconciliation', () => ({
   DEFAULT_UNATTENDED_CONFIDENCE_THRESHOLD: 0.9,
 }))
 
+// The balance mirror runs against cash_accounts after every successful sync;
+// its own behavior is covered in lib/cash-accounts/__tests__/service.test.ts.
+vi.mock('@/lib/cash-accounts/service', async () => {
+  const actual = await vi.importActual<typeof import('@/lib/cash-accounts/service')>(
+    '@/lib/cash-accounts/service',
+  )
+  return { ...actual, updateBalancesFromSync: vi.fn().mockResolvedValue(undefined) }
+})
+
 vi.mock('@/lib/email/service', () => ({
   getEmailService: () => ({ isConfigured: () => false, sendEmail: vi.fn() }),
 }))

app/api/extensions/enable-banking/sync/cron/route.ts

@@ -27,6 +27,7 @@ import { withCronContext } from '@/lib/api/with-cron-context'
 import { errorResponse, errorResponseFromCode } from '@/lib/errors/get-structured-error'
 import { getBranding } from '@/lib/branding/service'
 import { fetchAllRows } from '@/lib/supabase/fetch-all'
+import { updateBalancesFromSync } from '@/lib/cash-accounts/service'
 import type { StoredAccount } from '@/extensions/general/enable-banking/types'
 
 ensureInitialized()
@@ -324,6 +325,19 @@ export const GET = withCronContext('cron.bank_sync', async (_request, ctx) => {
           initial_sync_lookback_days: lookbackDays,
         }
       }
+      // Mirror refreshed balances into cash_accounts (what the Bank-page
+      // picker and reconciliation read); logs failures instead of throwing.
+      await updateBalancesFromSync(
+        supabase,
+        connection.company_id,
+        connection.id,
+        allAccounts.map(a => ({
+          external_uid: a.uid,
+          balance: a.balance,
+          available_balance: a.available_balance,
+          balance_updated_at: a.balance_updated_at,
+        })),
+      )
       await supabase
         .from('bank_connections')
         .update({