Add scheduled runs to all test workflows

[Copilot]

This PR extends the scheduled test approach to all workflows, ensuring that tests run regularly independent of PR activity.

Previously, only the ubuntu.yml and macos.yml workflows had scheduled runs, while the other test workflows (cvmfs_config_package.yml, cvmfs_http_proxy.yml, and cvmfs_repositories.yml) only ran on push and pull request events. This could cause unrelated test failures to block PRs when those tests hadn't been exercised recently.

Changes

Added scheduled runs to the following workflows:

• cvmfs_config_package.yml - now runs daily at 02:22 UTC
• cvmfs_http_proxy.yml - now runs daily at 01:11 UTC
• cvmfs_repositories.yml - now runs daily at 05:55 UTC

The cron schedules are distributed across different hours to avoid resource conflicts:

• 01:11 UTC - cvmfs_http_proxy
• 02:22 UTC - cvmfs_config_package
• 03:33 UTC - macos (existing)
• 04:44 UTC - ubuntu (existing)
• 05:55 UTC - cvmfs_repositories

All existing triggers (push and pull_request) are preserved, so the workflows continue to run on code changes as before.

Fixes #46.

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