feat: initialize monorepo structure with Bun and Turborepo

- Add package.json for the root with workspace configuration and scripts
- Create @gruperly/config package with TypeScript configuration
- Establish shared package @gruperly/shared with Zod schemas for validation
- Implement group, student, and payment schemas using Zod
- Set up TypeScript configuration for shared package
- Document stack architecture and technical specifications in stack.md
- Configure Turborepo with build, dev, lint, and typecheck tasks

apps/web/src/index.css

@@ -0,0 +1,39 @@
+@import "tailwindcss";
+
+@theme {
+  /* Colores de marca */
+  --color-background: #f8fafc;
+  --color-primary: #0a2540;
+  --color-primary-soft: #f0f4f9;
+  --color-accent: #1e90ff;
+  --color-accent-strong: #0088ff;
+  --color-accent-soft: #e6f4ff;
+  --color-foreground: #0f172a;
+
+  /* Badges de estado */
+  --color-success: #10b981;
+  --color-success-soft: #dcfce7;
+  --color-warning: #f59e0b;
+  --color-warning-soft: #fef3c7;
+  --color-danger: #ef4444;
+  --color-danger-soft: #fee2e2;
+  --color-border: #e2e8f0;
+
+  /* Border radius por defecto */
+  --radius-xl: 0.75rem;
+}
+
+@layer base {
+  :root {
+    color-scheme: light;
+  }
+
+  * {
+    @apply border-border;
+  }
+
+  body {
+    @apply bg-background text-primary antialiased;
+    min-height: 100dvh;
+  }
+}