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>

components/reconciliation/AccountOverview.tsx

@@ -470,6 +470,36 @@ export function AccountOverview({ account, rail, otherBankAccounts = [], window,
     },
   ]
 
+  // What the bank itself reports (F7): booked + available balance from the
+  // last PSD2 balance refresh, with its fetch date. Point-in-time, so it
+  // lives outside the movement-based tiles.
+  const bankReportedRaw =
+    !isSkv && !isManual
+      ? (status.bank as {
+          bank_reported_balance?: number | null
+          bank_reported_available_balance?: number | null
+          bank_balance_updated_at?: string | null
+        } | null)
+      : null
+  // Both the amount and its fetch timestamp must exist: a balance of unknown
+  // age labeled with today's date is exactly the misleading staleness the
+  // timestamp exists to prevent, so without it the line is omitted entirely.
+  const bankReportedLine =
+    bankReportedRaw &&
+    typeof bankReportedRaw.bank_reported_balance === 'number' &&
+    bankReportedRaw.bank_balance_updated_at
+      ? typeof bankReportedRaw.bank_reported_available_balance === 'number'
+        ? t('bank_reported_line_available', {
+            amount: formatCurrency(bankReportedRaw.bank_reported_balance, currency),
+            available: formatCurrency(bankReportedRaw.bank_reported_available_balance, currency),
+            date: formatDate(bankReportedRaw.bank_balance_updated_at),
+          })
+        : t('bank_reported_line', {
+            amount: formatCurrency(bankReportedRaw.bank_reported_balance, currency),
+            date: formatDate(bankReportedRaw.bank_balance_updated_at),
+          })
+      : null
+
   const unexplained = status.unexplained_difference
   const attn = status.stale
     ? t('stale_line', { source: sourceLabel })
@@ -535,6 +565,12 @@ export function AccountOverview({ account, rail, otherBankAccounts = [], window,
         ))}
       </div>
 
+      {bankReportedLine && (
+        <p className="text-[12.5px] text-muted-foreground" data-ph-mask>
+          {bankReportedLine}
+        </p>
+      )}
+
       {attn ? (
         <AttnLine>{attn}</AttnLine>
       ) : status.is_reconciled ? (