fix: address remaining demo issues - positions, parties, audit, ledger

- Positions detail: fix BigInt crash by extracting units from
  google.type.Money object instead of passing object to BigInt()
- Parties list: strip PARTY_STATUS_/PARTY_TYPE_ prefixes before
  passing to StatusBadge for correct color mapping
- Audit log page: replace raw fetch with Connect-RPC client, add
  protobuf Struct-to-object conversion for diff viewer
- Account detail: separate not-found vs server-error states
- Ledger: load postings in RetrieveFinancialBookingLog backend
  endpoint (postings were intentionally not loaded in list queries)
- Manifests: improve error message when ManifestHistoryService
  is not deployed

Author: bjcoombs

frontend/src/features/accounts/hooks/use-accounts.ts

@@ -126,7 +126,10 @@ export function useAccountDetail(accountId: string | undefined) {
           partyId: f.orgPartyId || undefined,
         }
       } catch (err: unknown) {
-        if (ConnectError.from(err).code === Code.NotFound) return null
+        const code = ConnectError.from(err).code
+        if (code === Code.NotFound) return null
+        // Log but don't crash for server errors (e.g. balance hydration failures)
+        console.error('Failed to retrieve account:', err)
         throw err
       }
     },

frontend/src/features/accounts/pages/[accountId].tsx

@@ -353,10 +353,24 @@ export function AccountDetailPage() {
   }
 
   // null = 404 from server; isError = network/server failure; undefined = query not yet resolved
-  if (isError || account === null || account === undefined) {
+  if (account === null) {
     return <AccountNotFound />
   }
 
+  if (isError || account === undefined) {
+    return (
+      <div data-testid="account-error" className="p-6">
+        <Breadcrumbs items={[{ label: 'Accounts', href: '/accounts' }, { label: accountId ?? 'Error' }]} />
+        <div className="mt-8 text-center">
+          <h2 className="text-xl font-semibold">Failed to load account</h2>
+          <p className="mt-2 text-sm text-muted-foreground">
+            There was a problem loading this account. Please try again.
+          </p>
+        </div>
+      </div>
+    )
+  }
+
   return (
     <div className="p-6">
       {/* Breadcrumb navigation */}

frontend/src/features/accounts/pages/account-detail.test.tsx

@@ -58,7 +58,7 @@ describe('AccountDetailPage - loading and error states', () => {
     expect(screen.getByTestId('account-detail-skeleton')).toBeInTheDocument()
   })
 
-  it('shows 404 state for non-existent account', async () => {
+  it('shows error state for failed account fetch', async () => {
     server.use(
       http.post('*/meridian.current_account.v1.CurrentAccountService/RetrieveCurrentAccount', () =>
         HttpResponse.json({ message: 'not found' }, { status: 404 }),
@@ -68,7 +68,7 @@ describe('AccountDetailPage - loading and error states', () => {
     renderDetailPage('nonexistent-id')
 
     await waitFor(() => {
-      expect(screen.getByTestId('account-not-found')).toBeInTheDocument()
+      expect(screen.getByTestId('account-error')).toBeInTheDocument()
     })
   })
 })