CI: migrate Ubuntu binary builds to Depot runners and remove save-disk-space usage

[Copilot]

This updates the server CI to use Depot runner types instead of default GitHub Ubuntu runners, aligned with the runner migration pattern used in gnosis_vpn-client. It also removes save-disk-space workflow usage from the build path.

• Runner migration (Ubuntu binary builds)

  • Switched Linux binary build runner targets to Depot:
    • depot-ubuntu-22.04-4
  • Applied in:
    • .github/workflows/build.yml
    • .github/workflows/merge.yaml
    • .github/workflows/release.yaml

• Reusable workflow input update

  • Updated manual workflow_dispatch runner option in .github/workflows/build-binaries.yaml to use Depot runner naming for Ubuntu builds.

• Save-disk-space cleanup

  • Removed save-disk-space workflow usage from the affected CI path (no remaining free-disk-space step references in current workflows).

Example of the runner change:

strategy:
  matrix:
    binary:
      - architecture: x86_64-linux
        runner: depot-ubuntu-22.04-4

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• depot.dev
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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