add: añadir iconos instalando la librería react-icons para los botones de login y logout.

ajustados márgenes en diferentes vistas para mantener coherencia visual.

frontend/package-lock.json

@@ -12,6 +12,7 @@
         "axios": "^1.13.6",
         "react": "^19.2.4",
         "react-dom": "^19.2.4",
+        "react-icons": "^5.6.0",
         "react-router-dom": "^7.13.2",
         "recharts": "^3.8.0",
         "tailwindcss": "^4.2.2"
@@ -3077,6 +3078,15 @@
         "react": "^19.2.4"
       }
     },
+    "node_modules/react-icons": {
+      "version": "5.6.0",
+      "resolved": "https://registry.npmjs.org/react-icons/-/react-icons-5.6.0.tgz",
+      "integrity": "sha512-RH93p5ki6LfOiIt0UtDyNg/cee+HLVR6cHHtW3wALfo+eOHTp8RnU2kRkI6E+H19zMIs03DyxUG/GfZMOGvmiA==",
+      "license": "MIT",
+      "peerDependencies": {
+        "react": "*"
+      }
+    },
     "node_modules/react-is": {
       "version": "19.2.4",
       "resolved": "https://registry.npmjs.org/react-is/-/react-is-19.2.4.tgz",