Rebrand to MyMidas

- Browser tab title: MyMidas
- Sidebar logo: Coins icon + MyMidas text
- Login page header: MyMidas
- TOTP issuer name: MyMidas (shows in authenticator apps)

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

frontend/src/components/layout/Sidebar.tsx

@@ -12,7 +12,7 @@ import {
   Settings,
   ChevronLeft,
   ChevronRight,
-  DollarSign,
+  Coins,
 } from "lucide-react";
 
 const navItems = [
@@ -39,9 +39,9 @@ export default function Sidebar() {
     >
       {/* Logo */}
       <div className="flex items-center h-16 px-4 border-b border-border shrink-0">
-        <DollarSign className="w-7 h-7 text-primary shrink-0" />
+        <Coins className="w-7 h-7 text-primary shrink-0" />
         {sidebarOpen && (
-          <span className="ml-2 font-semibold text-lg truncate">Finance</span>
+          <span className="ml-2 font-semibold text-lg truncate">MyMidas</span>
         )}
       </div>