fix: collapsed-sidebar logo expands the menu; crypto nav icon matches the rest

Collapsed sidebar had no way to expand except the button at the bottom —
the logo at the top was purely decorative. It's now a real button in that
state (expanded state unchanged, still non-interactive there).

Swapped the Crypto nav icon from Bitcoin (a filled coin-badge glyph) to
Coins — same thin line-icon style as the rest of the sidebar (Layers,
Target, Flag, ...), where Bitcoin's brand-logo shape stood out. Bitcoin
stays as-is elsewhere (holdings table row fallback, Net Worth breakdown) —
appropriate there as a specific-asset placeholder, this was only about the
nav item.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01855PiW5Wd8n4aRW4n9kByY

frontend/src/components/layout/Sidebar.tsx

@@ -94,10 +94,24 @@ export function Sidebar({ collapsed, onToggleCollapsed, mobileOpen, onCloseMobil
           collapsed ? "w-[72px]" : "w-56"
         )}
       >
-        <div className={cn("flex items-center gap-2 px-4 py-4", collapsed && "justify-center px-0")}>
-          <Logo size={24} />
-          {!collapsed && <span className="text-lg font-semibold tracking-tight text-text-primary">Aurum</span>}
-        </div>
+        {collapsed ? (
+          // Collapsed: the logo doubles as an "expand" button — the sidebar
+          // has no visible label to click in this state, so the icon itself
+          // needs to be the way back to the full menu.
+          <button
+            type="button"
+            onClick={onToggleCollapsed}
+            title={t("sidebar.expandMenu")}
+            className="flex items-center justify-center gap-2 px-0 py-4 hover:opacity-80"
+          >
+            <Logo size={24} />
+          </button>
+        ) : (
+          <div className="flex items-center gap-2 px-4 py-4">
+            <Logo size={24} />
+            <span className="text-lg font-semibold tracking-tight text-text-primary">Aurum</span>
+          </div>
+        )}
         <NavList collapsed={collapsed} />
         <div className="border-t border-border p-2.5">
           <button

frontend/src/lib/navigation.ts

@@ -1,8 +1,8 @@
 import {
   Activity,
   ArrowLeftRight,
-  Bitcoin,
   Calculator,
+  Coins,
   Flag,
   Layers,
   Lightbulb,
@@ -28,7 +28,7 @@ export interface NavItem {
 export const NAV_ITEMS: NavItem[] = [
   { labelKey: "nav.dashboard", to: "/", icon: LayoutDashboard },
   { labelKey: "nav.netWorth", to: "/net-worth", icon: TrendingUp },
-  { labelKey: "nav.crypto", to: "/crypto", icon: Bitcoin },
+  { labelKey: "nav.crypto", to: "/crypto", icon: Coins },
   { labelKey: "nav.roi", to: "/roi", icon: Calculator },
   { labelKey: "nav.transactions", to: "/transactions", icon: ArrowLeftRight },
   { labelKey: "nav.accounts", to: "/accounts", icon: Layers },