feat: every page follows the one-currency mode

Totals, info boxes, section headers, group subtotals, shares and the
per-currency charts on the dashboard, transactions, search, accounts,
merchants, statement, budgets, categories, tags, groups, piggy banks,
reports and the category, tag, budget and merchant pages sum into one
converted amount when the mode is on; charts split by currency merge
into one lane. Inputs, reconciliation and the Foreign column stay exact.

Money moved to or from a debt, loan or mortgage no longer counts as
income or spending in the transaction list boxes; it shows as From
debts and To debts. The running balance of an incoming foreign-currency
transfer shows in the account's currency.

src/lib/components/reports/AccountBalances.svelte

@@ -1,7 +1,9 @@
 <script lang="ts">
   import { createQuery } from "@tanstack/svelte-query";
+  import { displayCode, inDisplay } from "#lib/reports/display.js";
   import { reportQueries } from "#lib/reports/queries.js";
   import {
+    displayMoney,
     drillQuery,
     money,
     navigate,
@@ -34,12 +36,15 @@
       .sort((a, b) => a.name.localeCompare(b.name));
   });
   const sums = $derived.by(() => {
+    const into = displayCode(new Set(rows.map((row) => row.code)));
     const map = new Map<string, { start: number; end: number }>();
     for (const row of rows) {
-      const sum = map.get(row.code) ?? { end: 0, start: 0 };
-      sum.start += row.start;
-      sum.end += row.end;
-      map.set(row.code, sum);
+      const start = inDisplay(row.start, row.code, into);
+      const end = inDisplay(row.end, row.code, into);
+      const sum = map.get(start.code) ?? { end: 0, start: 0 };
+      sum.start += start.amount;
+      sum.end += end.amount;
+      map.set(start.code, sum);
     }
     const order = report.codes;
     return [...map.entries()].sort(
@@ -106,10 +111,14 @@
                 {row.name}
               </button>
             </td>
-            <td class="num px-3 text-right">{money(row.code, row.start)}</td>
-            <td class="num px-3 text-right">{money(row.code, row.end)}</td>
+            <td class="num px-3 text-right">
+              {displayMoney(row.code, row.start)}
+            </td>
+            <td class="num px-3 text-right">
+              {displayMoney(row.code, row.end)}
+            </td>
             <td class="num px-3 text-right {tone(row.end - row.start)}">
-              {money(row.code, row.end - row.start, true)}
+              {displayMoney(row.code, row.end - row.start, true)}
             </td>
           </tr>
         {/each}