feat: show every amount in one currency, chosen in the header, $ toggles it

A selector in the header and the palette's Currency group pick the
currency, the primary one by default; the choice persists between pages
and $ switches it on and off. Rates come from Firefly's exchange rates,
then from the owner's own transactions with a foreign amount, walking
through other currencies when there is no direct pair. Amount converts
with a ≈ and keeps the original in its title; Money sums several
currencies into one converted amount.

src/routes/+page.svelte

@@ -14,30 +14,11 @@
   import PiggyBanksBox from "#lib/components/dashboard/PiggyBanksBox.svelte";
   import SubscriptionsBox from "#lib/components/dashboard/SubscriptionsBox.svelte";
   import PageHeader from "#lib/components/shell/PageHeader.svelte";
-  import Checkbox from "#lib/components/ui/checkbox/checkbox.svelte";
   import { provideColumn } from "#lib/dashboard/column.svelte.js";
-  import { inPrimary, ratesQuery } from "#lib/dashboard/primary.svelte.js";
-  import { useKeys } from "#lib/keys.svelte.js";
   import { period } from "#lib/period.svelte.js";
-  import { session } from "#lib/session.svelte.js";
 
   provideColumn();
 
-  const rates = createQuery(() => ratesQuery());
-  const primary = $derived(session.primary?.code ?? "");
-  const ownRates = $derived(
-    inPrimary.on && Object.values(rates.data ?? {}).some((r) => r.own)
-  );
-
-  useKeys(() => [
-    {
-      group: "Dashboard",
-      keys: "$",
-      label: `Show totals in ${primary}`,
-      run: () => inPrimary.toggle(),
-    },
-  ]);
-
   const assets = createQuery(() =>
     accountsQuery("asset", period.start, period.end)
   );
@@ -49,22 +30,7 @@
   });
 </script>
 
-<PageHeader subtitle="What's playing?" title="Dashboard">
-  {#snippet actions()}
-    <div class="flex items-center gap-1.5 text-[12px] text-cladd-fg-soft">
-      <Checkbox
-        checked={inPrimary.on}
-        id="in-primary"
-        onCheckedChange={() => inPrimary.toggle()}
-      />
-      <label for="in-primary">Show in {primary}</label>
-      <span class="hidden sm:inline"><span class="kbd">$</span></span>
-      {#if ownRates}
-        <span>≈ from your own exchanges</span>
-      {/if}
-    </div>
-  {/snippet}
-</PageHeader>
+<PageHeader subtitle="What's playing?" title="Dashboard" />
 
 <InfoBoxes />