Display of start times in Daily Plan view should consider time zone

Current Situation

• The display of start times with the daily plan is wrong.
• Consider the CreateDailyPlan order:

  <order>
    <params>
      <param name="day_offset" value="31"/>
    </params>
    <run_time>
      <weekdays>
        <day day="1 2 3 4 5 6 7">
          <period single_start="00:00:00"/>
        </day>
      </weekdays>
    </run_time>
  </order>
  

  _

• The order is intended to start at midnight each day.
• When running this order then the daily_plan table shows a start date of 22:00:00 for each day (columns planned_start, expected_end) which is correct for the Europe/Berlin time zone which is UTC+2, i.e. the display date for 22:00 would be 00:00
• In fact the display date is 22:00, i.e. the user browser time zone is not considered.
• In addition the Daily Plan view shows entries for wrong dates if the "Today" and "Next 24 hours" buttons are pressed repeatedly.

Desired Behavior

• The user browser time zone should be considered in the Daily Plan view.

Maintainer Notes

• The behavior is due to older entries in the daily plan table that had been created with previous releases.
• Purging the daily plan table in the database resolves the issue.