Update GitHub Artifact Actions

Author: renovate[bot]

.github/workflows/build-preview.yml

@@ -19,7 +19,7 @@ jobs:
             - run: bun install
             - run: cd web && bun run build
             - name: "upload build artifact"
-              uses: "actions/upload-artifact@v4"
+              uses: "actions/upload-artifact@v5"
               with:
                   name: "preview-build"
                   path: |

.github/workflows/deploy-preview.yml

@@ -19,7 +19,7 @@ jobs:
         name: "Deploy Preview to Cloudflare Pages"
         steps:
             - name: "Download build artifact"
-              uses: "actions/download-artifact@v5"
+              uses: "actions/download-artifact@v6"
               id: "preview-build-artifact"
               with:
                   name: "preview-build"