feat(FN-005): implement frontend foundation with auth and routing

- Add OIDC authentication with PKCE flow
- Create dashboard shell with sidebar and header
- Implement project management UI (list, create, detail)
- Add tool spawn page with tool/project selection
- Create tool instance detail page with status and controls
- Set up React Router with route guards
- Add Zustand auth store and API client with types

apps/web/src/index.css

@@ -1,3 +1,21 @@
+@import "tailwindcss";
+
+@theme {
+  --color-bg: #0f172a;
+  --color-fg: #e2e8f0;
+  --color-accent: #38bdf8;
+  --color-surface: rgba(255, 255, 255, 0.04);
+  --color-border: rgba(255, 255, 255, 0.08);
+  --color-border-subtle: rgba(255, 255, 255, 0.06);
+  --spacing-xs: 0.5rem;
+  --spacing-sm: 1rem;
+  --spacing-md: 1.5rem;
+  --spacing-lg: 2rem;
+  --spacing-xl: 2.5rem;
+  --radius-default: 0.75rem;
+  --font-family-base: system-ui, -apple-system, Segoe UI, Roboto, Ubuntu, Cantarell, Noto Sans, sans-serif;
+}
+
 :root {
   --bg: #0f172a;
   --fg: #e2e8f0;