Add .def file for R 4.6.0 with rv and Quarto installation

[MVesuviusC]

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[Copilot]

Pull request overview

Adds a new Apptainer/Singularity definition to build an R 4.6.0-based container image that includes the rv R package manager and Quarto, consistent with the existing R 4.4.3 container definition.

Changes:

• Introduces a new r4.6.0.def definition bootstrapped from rocker/r-ver:4.6.0
• Installs rv (v0.21.0) and Quarto (1.9.37), and wires them into /usr/local/bin
• Adds environment variables and a %test section to validate installed tool versions

Comments suppressed due to low confidence (1)

r4.6.0.def:44

• Quarto is downloaded and installed without any integrity verification (no checksum/signature validation). Please add a SHA256/SHA512 verification step (or signature verification if available) before extracting to reduce supply-chain risk during builds.

    wget https://github.com/quarto-dev/quarto-cli/releases/download/v${QUARTO_VERSION}/quarto-${QUARTO_VERSION}-linux-amd64.tar.gz
    
    mkdir -p /opt/quarto/${QUARTO_VERSION}
    tar xzf \
        quarto-${QUARTO_VERSION}-linux-amd64.tar.gz \
        -C /opt/quarto/${QUARTO_VERSION} \
        --strip-components=1

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