Initial commit: Plataforma de Economía

Features:
- React 18 + TypeScript frontend with Vite
- Go + Gin backend API
- PostgreSQL database
- JWT authentication with refresh tokens
- User management (admin panel)
- Docker containerization
- Progress tracking system
- 4 economic modules structure

Fixed:
- Login with username or email
- User creation without required email
- Database nullable timestamps
- API response field naming

frontend/src/index.css

@@ -0,0 +1,54 @@
+@tailwind base;
+@tailwind components;
+@tailwind utilities;
+
+* {
+  margin: 0;
+  padding: 0;
+  box-sizing: border-box;
+}
+
+body {
+  font-family: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
+  -webkit-font-smoothing: antialiased;
+  -moz-osx-font-smoothing: grayscale;
+}
+
+@layer utilities {
+  .text-primary {
+    @apply text-blue-600;
+  }
+  .bg-primary {
+    @apply bg-blue-600;
+  }
+  .hover\:bg-primary:hover {
+    @apply bg-blue-700;
+  }
+  .focus\:ring-primary:focus {
+    --tw-ring-color: rgb(37 99 235);
+  }
+  .bg-success {
+    @apply bg-emerald-500;
+  }
+  .text-success {
+    @apply text-emerald-500;
+  }
+  .bg-secondary {
+    @apply bg-violet-600;
+  }
+  .text-secondary {
+    @apply text-violet-600;
+  }
+  .bg-warning {
+    @apply bg-amber-500;
+  }
+  .text-warning {
+    @apply text-amber-500;
+  }
+  .bg-error {
+    @apply bg-red-500;
+  }
+  .text-error {
+    @apply text-red-500;
+  }
+}