Fixes #8154

/claim #8154

Changes

• Add dynamic Docker APT repo codename fallback in InstallDocker.php: when VERSION_CODENAME (e.g. trixie for Debian 13) doesn’t exist in Docker’s APT repo, automatically fall back to bookworm. This is future-proof — once Docker adds trixie support, the fallback stops being used.
• Add Alpine Linux prerequisite handler in InstallPrerequisites.php using apk — Alpine was listed in SUPPORTED_OS but had no handler, causing the “Unsupported OS type” error.
• Add Alpine Linux Docker install handler using apk and OpenRC service management.
• Make Docker enable/restart commands compatible with both systemd and OpenRC init systems.

Testing

• Verified PHP syntax of both modified files
• Confirmed Debian 13 (ID=debian) already matches existing SUPPORTED_OS constant — no changes needed there
• Verified the dynamic repo check approach works: curl --head against Docker’s repo returns 404 for missing codenames, triggering the bookworm fallback
• All changes follow existing code patterns for other OS handlers (RHEL, SLES, Arch)