Clean up codebase and prepare as template

Remove unused files and code:
- Delete test/debug endpoints (test.get.ts, public.get.ts, user.get.ts, debug-config backup)
- Remove unused OAuth wrapper (oauth-authentik.ts)
- Clean up debug console.log statements
- Simplify code comments

Fix TypeScript errors:
- Add @types/node dependency
- Create index.d.ts with User interface extension
- Fix UButton color props (red→error, gray→neutral)
- Add type assertions in protected.get.ts

Update documentation:
- Enhance README.md as template documentation
- Update SETUP.md with correct API routes (/api/auth/* instead of /auth/*)
- Add NUXT_OAUTH_AUTHENTIK_SERVER_URL_INTERNAL documentation
- Update endpoint documentation

This commit prepares the repository to be used as a template for future Nuxt 4 + Authentik OAuth projects.

nuxt4-app/package-lock.json

@@ -14,6 +14,9 @@
         "typescript": "^5.9.3",
         "vue": "^3.5.22",
         "vue-router": "^4.5.1"
+      },
+      "devDependencies": {
+        "@types/node": "^24.7.2"
       }
     },
     "node_modules/@adonisjs/hash": {
@@ -5205,6 +5208,16 @@
       "integrity": "sha512-dWHzHa2WqEXI/O1E9OjrocMTKJl2mSrEolh1Iomrv6U+JuNwaHXsXx9bLu5gG7BUWFIN0skIQJQ/L1rIex4X6w==",
       "license": "MIT"
     },
+    "node_modules/@types/node": {
+      "version": "24.7.2",
+      "resolved": "https://registry.npmjs.org/@types/node/-/node-24.7.2.tgz",
+      "integrity": "sha512-/NbVmcGTP+lj5oa4yiYxxeBjRivKQ5Ns1eSZeB99ExsEQ6rX5XYU1Zy/gGxY/ilqtD4Etx9mKyrPxZRetiahhA==",
+      "devOptional": true,
+      "license": "MIT",
+      "dependencies": {
+        "undici-types": "~7.14.0"
+      }
+    },
     "node_modules/@types/parse-path": {
       "version": "7.0.3",
       "resolved": "https://registry.npmjs.org/@types/parse-path/-/parse-path-7.0.3.tgz",
@@ -13680,6 +13693,13 @@
         "node": ">=20.18.1"
       }
     },
+    "node_modules/undici-types": {
+      "version": "7.14.0",
+      "resolved": "https://registry.npmjs.org/undici-types/-/undici-types-7.14.0.tgz",
+      "integrity": "sha512-QQiYxHuyZ9gQUIrmPo3IA+hUl4KYk8uSA7cHrcKd/l3p1OTpZcM0Tbp9x7FAtXdAYhlasd60ncPpgu6ihG6TOA==",
+      "devOptional": true,
+      "license": "MIT"
+    },
     "node_modules/unenv": {
       "version": "2.0.0-rc.21",
       "resolved": "https://registry.npmjs.org/unenv/-/unenv-2.0.0-rc.21.tgz",