feat: Rebrand frontend from Patherly to ResolutionFlow

- Add brand assets (favicon, icons, logos) to public/icons and src/assets/brand
- Update index.html with new favicon, title, meta, Google Fonts (Plus Jakarta Sans, Inter, Outfit)
- Add brand colors, font families, and gradient utilities to Tailwind config
- Replace CSS variables with purple-tinted theme for both light and dark modes
- Create reusable BrandLogo and BrandWordmark components
- Update AppLayout header with logo and wordmark
- Update LoginPage and RegisterPage with branded logo, wordmark, and gradient buttons
- Replace all remaining "Patherly" references in SettingsPage

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/components/common/BrandWordmark.tsx

@@ -0,0 +1,25 @@
+import { cn } from '@/lib/utils'
+
+interface BrandWordmarkProps {
+  size?: 'sm' | 'lg'
+  className?: string
+}
+
+/**
+ * ResolutionFlow wordmark with gradient "Flow" text.
+ * sm for header/navbar, lg for login/register pages.
+ */
+export function BrandWordmark({ size = 'sm', className }: BrandWordmarkProps) {
+  return (
+    <span
+      className={cn(
+        'font-heading font-bold',
+        size === 'sm' ? 'text-xl' : 'text-3xl tracking-tight',
+        className
+      )}
+    >
+      <span className="text-foreground">Resolution</span>
+      <span className="text-gradient-brand">Flow</span>
+    </span>
+  )
+}