fix(devcontainer): apply full OS upgrade to remediate base image CVEs (#32)

* fix: upgrade gnupg/keyboxd packages to patch CVE-2025-68973

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Co-authored-by: idvoretskyi <118459+idvoretskyi@users.noreply.github.com>

* fix: use apt-get -y upgrade to patch all vulnerabilities in devcontainer image

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---------

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Co-authored-by: idvoretskyi <118459+idvoretskyi@users.noreply.github.com>

Author: Copilot

.devcontainer/Dockerfile

@@ -9,5 +9,6 @@ RUN apt-get update && export DEBIAN_FRONTEND=noninteractive \
     sudo \
     linux-libc-dev \
     vim-tiny \
+    && apt-get -y upgrade \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/*