Add centralized API client with axios interceptors, remove vue-axios

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -39,7 +39,6 @@
     "primevue": "^4.5.4",
     "tippy.js": "^6.3.7",
     "vue": "^3.5.29",
-    "vue-axios": "^3.5.2",
     "vue-chartjs": "^5.3.3",
     "vue-router": "^5.0.3",
     "vue-sweetalert2": "^5.0.11",