refactor(frontend): migracion a Mantine y limpieza de widgets

- Migra el frontend a Mantine v9 siguiendo la regla de theming del registry (@fn_library, sin Tailwind/cn/CVA).
- Reescribe DashboardShell, FilterBar, Section, WidgetRenderer y todos los widgets (Area/Bar/Line/Pie/KPI/Sparkline/Table) con componentes y props de Mantine.
- Ajusta vite.config, main.tsx, App.tsx, app.css y env.d.ts.
- Añade postcss.config.cjs requerido por Mantine.
- Actualiza package.json y pnpm-lock.
- Ajusta config.go, main.go y los ejemplos (fn_registry_apps/overview) para el nuevo esquema de tipos en frontend/src/types.ts.

frontend/package.json

@@ -9,27 +9,25 @@
     "preview": "vite preview --host"
   },
   "dependencies": {
-"@base-ui/react": "^1.3.0",
+    "@mantine/charts": "^9.0.0",
+    "@mantine/core": "^9.0.0",
+    "@mantine/hooks": "^9.0.0",
+    "@mantine/notifications": "^9.0.0",
     "@phosphor-icons/react": "^2.1.10",
-    "@radix-ui/react-checkbox": "^1.3.3",
-    "@radix-ui/react-slider": "^1.3.6",
+    "@tabler/icons-react": "^3.41.1",
     "@tanstack/react-table": "^8.21.3",
-    "class-variance-authority": "^0.7.1",
-    "clsx": "^2.1.1",
     "date-fns": "^4.1.0",
-    "lucide-react": "^0.577.0",
     "react": "^19.2.4",
-    "react-day-picker": "^9.14.0",
     "react-dom": "^19.2.4",
-    "recharts": "^3.8.0",
-    "tailwind-merge": "^3.5.0"
+    "recharts": "^3.8.0"
   },
   "devDependencies": {
-    "@tailwindcss/vite": "^4.2.2",
     "@types/react": "^19.2.14",
     "@types/react-dom": "^19.2.3",
     "@vitejs/plugin-react": "^6.0.0",
-    "tailwindcss": "^4.2.2",
+    "postcss": "^8.5.8",
+    "postcss-preset-mantine": "^1.18.0",
+    "postcss-simple-vars": "^7.0.1",
     "typescript": "~5.9.3",
     "vite": "^8.0.0"
   }