feat: [US-001] - Project scaffolding and configuration

- Initialize Next.js 16 with TypeScript and App Router
- Configure TailwindCSS 4 via @tailwindcss/postcss
- Install Supabase client libraries (@supabase/supabase-js, @supabase/ssr)
- Create .env.example with required environment variables
- Set up basic folder structure: src/app, src/components, src/lib, src/types

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

src/app/globals.css

@@ -0,0 +1,26 @@
+@import "tailwindcss";
+
+:root {
+  --background: #ffffff;
+  --foreground: #171717;
+}
+
+@theme inline {
+  --color-background: var(--background);
+  --color-foreground: var(--foreground);
+  --font-sans: var(--font-geist-sans);
+  --font-mono: var(--font-geist-mono);
+}
+
+@media (prefers-color-scheme: dark) {
+  :root {
+    --background: #0a0a0a;
+    --foreground: #ededed;
+  }
+}
+
+body {
+  background: var(--background);
+  color: var(--foreground);
+  font-family: Arial, Helvetica, sans-serif;
+}