on the main pedalp page, start the events list from "today"

[ionous]

pp pages specify event list options using a start and end date, for example: https://github.com/shift-org/shift-docs/blob/2c826225f8ed506b3a3128b6bc42922bef259b07/site/content/pedalpalooza-calendar.md?plain=1#L9

this pr changes main.js viewEvents() ( which builds the event list ) so that:

1. when today's date is in that range, the list will use "today" as the start, and still use the specified end. ( previously it used "start" )
2. when today isnt in that range ( archive pp pages ), it uses the specified start, and still use the specified end. ( same as old behavior )
3. when there isn't a start and end range, like for the /calendar view, it uses today as start, and today + a constant as the end. ( same as old behavior )

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code changes:

• moved start date calculations to a function getInitialView(), and put the results in a "view" object to simplify the code some.
• switched to dayjs:
  • daysAfter() isnt needed, now just: .add();
  • timezoneOffset isnt needed, now just: .utc()
  • new Date() is dayjs()
• when "today" is in the start/end range, getInitialView() uses "today" as the start; all other decisions are the same.
• switched from using'something' in options to options.something: the logic is the same for our use cases, and it reads better the more modern way.
• removed the var isExpanded, instead the view object has property show_details (which is whatgetEventHTML needs. )
• getEventsHTML() only works if called with id or start/end date; so i added an explicit error to make that failure more obvious. ( doesn't affect any current pages b/c they all do the right thing. )