refactor: migrate frontend from shadcn/Tailwind to Mantine v9

Reescribe todos los componentes UI para usar Mantine v9 en lugar de shadcn/Tailwind.
Elimina cn(), CVA, components.json, theme_provider custom y globals.css con Tailwind.
Añade 25+ componentes nuevos (AppShell, AuthForm, DatePickerInput, Dropzone, etc.)
y MantineProvider como wrapper estándar del sistema de temas.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/package.json

@@ -6,36 +6,38 @@
   "scripts": {
     "dev": "vite",
     "build": "tsc && vite build",
-    "preview": "vite preview",
-    "add": "pnpm dlx shadcn@latest add"
+    "preview": "vite preview"
   },
   "keywords": [],
   "author": "",
   "license": "ISC",
   "packageManager": "pnpm@10.17.0",
   "dependencies": {
-    "@base-ui/react": "^1.3.0",
     "@fontsource-variable/geist": "^5.2.8",
-    "class-variance-authority": "^0.7.1",
-    "clsx": "^2.1.1",
+    "@mantine/charts": "^9.0.0",
+    "@mantine/core": "^9.0.0",
+    "@mantine/dates": "^9.0.1",
+    "@mantine/dropzone": "^9.0.1",
+    "@mantine/form": "^9.0.0",
+    "@mantine/hooks": "^9.0.0",
+    "@mantine/notifications": "^9.0.0",
+    "@tabler/icons-react": "^3.41.1",
+    "dayjs": "^1.11.20",
     "graphology": "^0.26.0",
     "graphology-layout-forceatlas2": "^0.10.1",
     "graphology-types": "^0.24.8",
-    "lucide-react": "^1.7.0",
     "react": "^19.2.4",
     "react-dom": "^19.2.4",
     "recharts": "^3.8.1",
-    "shadcn": "^4.1.1",
-    "sigma": "^3.0.2",
-    "tailwind-merge": "^3.5.0",
-    "tw-animate-css": "^1.4.0"
+    "sigma": "^3.0.2"
   },
   "devDependencies": {
-    "@tailwindcss/vite": "^4.2.2",
     "@types/react": "^19.2.14",
     "@types/react-dom": "^19.2.3",
     "@vitejs/plugin-react": "^6.0.1",
-    "tailwindcss": "^4.2.2",
+    "postcss": "^8.5.8",
+    "postcss-preset-mantine": "^1.18.0",
+    "postcss-simple-vars": "^7.0.1",
     "tsx": "^4.21.0",
     "typescript": "^6.0.2",
     "vite": "^8.0.3"