fix(docker): improve startup process and SIGTERM handling

[dezhishen]

Close #1032

This issue was introduced in #791

[Copilot]

Pull Request Overview

This PR modifies the CI startup process by changing how the OpenList service is initialized, removing the previous directory copying mechanism and switching to direct execution of the OpenList server command.

• Removes the OpenList directory copying logic that was previously used for service initialization
• Changes from using runsvdir to directly executing the OpenList server command
• Moves the runsvdir execution to run in the background only when aria2 is enabled

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