[WIP] Fix failing GitHub Actions job pack-charm

[Copilot]

• Inspect failing pack-charm GitHub Actions job logs and identify root cause
• Locate charm packaging configuration used by pack-charm
• Run baseline relevant lint/test/build commands before making changes
• Apply minimal fix for missing rustup in charm build environment
• Run targeted validation for modified files
• Run security/quality validation and summarize results

[webteam-app]

Copilot is not a collaborator of the repo