chore: upgrade docs to Astro 6

Author: HDauven

.github/workflows/validate_links.yml

@@ -14,6 +14,6 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
         with:
-          node-version: 22
-      - run: npm install
+          node-version: 22.12.0
+      - run: npm ci
       - run: npm run build

.gitignore

@@ -15,7 +15,6 @@ pnpm-debug.log*
 # environment variables
 .env
 .env.production
-.nvmrc
 
 # macOS-specific files
 .DS_Store

.nvmrc

@@ -0,0 +1 @@
+22.12.0