design overhaul + expenses page

- Stripe-style theme: single indigo (#635BFF) brand, 6px radius,
  Inter scale; rewritten themePrimitives + MUI customizations
  (solid primary, near-black secondary, severity-aware Alert)
- Sticky Header (brand-left nav, theme toggle, mobile drawer),
  inline Footer, route fade-in, per-route document.title
- Home hero + feature cards (dead /dashboard,/reports links replaced)
- Split-panel AuthPage with validation and password visibility
- Data pages: PageHeader/EmptyState, breadcrumbed Fetch Request
  pages, admin table polish (numeric alignment, row-hover actions,
  skeletons, empty states), single-accent admin SideMenu
- Global ToastProvider wired into app shell
- New /expenses page: month-grouped feed, single-open accordion
  with inline detail (account, tags, amount, timestamps)

src/shared-theme/customizations/surfaces.ts

@@ -36,7 +36,7 @@ export const surfacesCustomizations: Components<Theme> = {
     styleOverrides: {
       root: ({ theme }) => ({
         border: 'none',
-        borderRadius: 8,
+        borderRadius: (theme.vars || theme).shape.borderRadius,
         '&:hover': { backgroundColor: gray[50] },
         '&:focus-visible': { backgroundColor: 'transparent' },
         ...theme.applyStyles('dark', {