Fix: Repair randomized timer for first-time intranet updates

[qiuzhiqian]

• When switching from public network to intranet, force-refresh the timer with a randomized value.
• Use a randomized value for the initial timer upon each restart, then switch to fixed values for subsequent timer initiations

Bug: https://pms.uniontech.com/bug-view-355587.html

[github-actions]

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[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: qiuzhiqian, zhaohuiw42

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