Make apt noninteractive and use apt-get for installs

[gregorkrebs]

Motivation

• Ensure unattended runs of setup.sh do not prompt for input by enforcing noninteractive apt behavior.
• Provide an opt-in lean install via --no-install-recommends and a reusable flag set for installs.
• Unify package manager usage to apt-get and resolve the prior mixed/incorrect flag placement that caused a merge conflict.

Description

• Export DEBIAN_FRONTEND=noninteractive and add APT_INSTALL_FLAGS with a default of (-y) plus support for APT_NO_INSTALL_RECOMMENDS=1 to append --no-install-recommends.
• Replace apt install/upgrade invocations with apt-get and use sudo apt-get -y upgrade for noninteractive upgrades.
• Remove apt-transport-https from the initial requirements list and update all install commands to include ${APT_INSTALL_FLAGS[@]}.
• Update the per-PHP-version install loop to pass "${APT_INSTALL_FLAGS[@]}" uniformly so flags are applied consistently.

Testing

• No automated tests were run for this change.

---

Codex Task