ci: install bun from the npm registry (GitHub release assets answer 504 now and then), bun.sh with retries as fallback

.forgejo/workflows/acceptance.yml

@@ -33,7 +33,7 @@ jobs:
         if: ${{ matrix.platform == 'Linux' }}
         shell: bash
         run: |
-          curl -fsSL https://bun.sh/install | bash -s "bun-v${BUN_VERSION}" >/dev/null
+          bash tools/ci-install-bun.sh
           echo "$HOME/.bun/bin" >> "${FORGEJO_PATH:-$GITHUB_PATH}"
       - name: Acceptance matrix (Linux)
         if: ${{ matrix.platform == 'Linux' }}
@@ -97,7 +97,7 @@ jobs:
           path: acceptance-runs/Windows-bun
       - name: Matrix (markdown), red cells fail the job
         run: |
-          curl -fsSL https://bun.sh/install | bash -s "bun-v${BUN_VERSION}" >/dev/null
+          bash tools/ci-install-bun.sh
           export PATH="$HOME/.bun/bin:$PATH"
           V=$(bun tools/desktop-version.ts --print)
           mkdir -p out