Add Zod for parsing event data (OFC-1)

[davish]

Closes #248.

Zod lets us define the type of an OFCEvent and how it's parsed at the same time. As an added bonus, Zod makes it easy to parse values that are stored as strings such as date and start into relevant types during parsing rather than doing it at every callsite where those types are needed. This will make querying on date ranges in #326 easier.

• Define Zod schema for OFCEvent
• Add tests to make sure events are parsed properly.
• Assert that the old OFCEvent and new OFCEvent are equivalent types.
• Remove old OFCEvent and validateEvent().
• Fix daily note dragging bug
• Define Zod schema for CalendarInfo
• [Optional] Parse strings into luxon dates and times and add serialization methods that turn them back in to primitive types. Might leave this for another PR.

[davish]

Looks like there's a bug where events in daily notes are duplicated in the view when they're moved to a new day. Those old events aren't in the eventstore, and so get "event not found" errors when you then try and modify them. Likely this is something to do with the event ID not propagating through? Will investigate. It's not present on main, just this branch.

Potentially related to the type changes in the DailyNoteCalendar.