Include investment holding values in net worth and account balances

- Net worth report, balance sheet, and daily snapshots now add holding
  market values (falling back to cost basis) to investment-type account
  balances (investment, pension, stocks_shares_isa, crypto_wallet)
- Accounts list shows total value for investment accounts with a
  breakdown line ("£X cash + £Y holdings") when both are non-zero
- Add Holding modal gains a "Debit account for this purchase" toggle
  that creates a matching withdrawal transaction, enabling proper cash
  flow tracking for users who fund their brokerage via transfer first
- Both simple (holdings-only) and full cash-flow workflows produce
  correct net worth figures without double-counting

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/pages/accounts/AccountList.tsx

@@ -2,6 +2,7 @@ import { useState } from "react";
 import { Link } from "react-router-dom";
 import { useQuery, useMutation, useQueryClient } from "@tanstack/react-query";
 import { getAccounts, createAccount, updateAccount, deleteAccount, getNetWorth, type Account } from "@/api/accounts";
+import { getPortfolio } from "@/api/investments";
 import { formatCurrency } from "@/utils/currency";
 import { cn } from "@/utils/cn";
 import {
@@ -57,6 +58,17 @@ export default function AccountList() {
     queryFn: getNetWorth,
   });
 
+  const { data: portfolio } = useQuery({
+    queryKey: ["portfolio"],
+    queryFn: getPortfolio,
+  });
+
+  const holdingValueByAccount = (portfolio?.holdings ?? []).reduce<Record<string, number>>((acc, h) => {
+    const v = Number(h.current_value || h.cost_basis_total);
+    acc[h.account_id] = (acc[h.account_id] ?? 0) + v;
+    return acc;
+  }, {});
+
   const invalidate = () => {
     qc.invalidateQueries({ queryKey: ["accounts"] });
     qc.invalidateQueries({ queryKey: ["net-worth"] });
@@ -129,6 +141,7 @@ export default function AccountList() {
           accounts={assets}
           onEdit={setEditing}
           onDelete={id => deleteMutation.mutate(id)}
+          holdingValueByAccount={holdingValueByAccount}
         />
       )}
 
@@ -147,6 +160,7 @@ export default function AccountList() {
           accounts={inactive}
           onEdit={setEditing}
           onDelete={id => deleteMutation.mutate(id)}
+          holdingValueByAccount={holdingValueByAccount}
           muted
         />
       )}
@@ -179,17 +193,21 @@ export default function AccountList() {
   );
 }
 
+const INVESTMENT_TYPES = new Set(["investment", "pension", "stocks_shares_isa", "crypto_wallet"]);
+
 function AccountGroup({
   title,
   accounts,
   onEdit,
   onDelete,
+  holdingValueByAccount = {},
   muted = false,
 }: {
   title: string;
   accounts: Account[];
   onEdit: (a: Account) => void;
   onDelete: (id: string) => void;
+  holdingValueByAccount?: Record<string, number>;
   muted?: boolean;
 }) {
   return (
@@ -243,14 +261,31 @@ function AccountGroup({
                 </div>
 
                 <div className="text-right shrink-0">
-                  <p className={cn("font-semibold tabular-nums", isLiability ? "text-destructive" : "text-foreground")}>
-                    {formatCurrency(account.current_balance, account.currency)}
-                  </p>
-                  {account.credit_limit != null && (
-                    <p className="text-xs text-muted-foreground">
-                      limit {formatCurrency(account.credit_limit, account.currency)}
-                    </p>
-                  )}
+                  {(() => {
+                    const holdingVal = INVESTMENT_TYPES.has(account.type) ? (holdingValueByAccount[account.id] ?? 0) : 0;
+                    const cashBal = Number(account.current_balance);
+                    const total = cashBal + holdingVal;
+                    return (
+                      <>
+                        <p className={cn("font-semibold tabular-nums", isLiability ? "text-destructive" : "text-foreground")}>
+                          {formatCurrency(holdingVal > 0 ? total : cashBal, account.currency)}
+                        </p>
+                        {holdingVal > 0 && cashBal !== 0 && (
+                          <p className="text-xs text-muted-foreground">
+                            {formatCurrency(cashBal, account.currency)} cash + {formatCurrency(holdingVal, account.currency)} holdings
+                          </p>
+                        )}
+                        {holdingVal > 0 && cashBal === 0 && (
+                          <p className="text-xs text-muted-foreground">holdings value</p>
+                        )}
+                        {account.credit_limit != null && (
+                          <p className="text-xs text-muted-foreground">
+                            limit {formatCurrency(account.credit_limit, account.currency)}
+                          </p>
+                        )}
+                      </>
+                    );
+                  })()}
                 </div>
 
                 <div className="flex items-center gap-1 opacity-100 sm:opacity-0 sm:group-hover:opacity-100 transition-opacity shrink-0">