fix: Calendar timezone day-shift bug (#7048)

[domocarroll]

Summary

Fixes #7048 - Calendar events appearing shifted by one day.

Problem

Events scheduled for today were appearing in tomorrow's column. The toCalendar function in DayCalendar.svelte used raw millisecond arithmetic (MILLISECONDS_IN_DAY * day + date.getTime()) which doesn't handle timezone transitions properly when combined with setHours().

Solution

• Replace millisecond arithmetic with Date.setDate() for proper calendar day calculations
• Fix mutation bug where the date parameter was being modified directly

Changes

- const startDay = new Date(MILLISECONDS_IN_DAY * day + date.getTime()).setHours(0, 0, 0, 0)
+ const targetDay = new Date(date)
+ targetDay.setDate(targetDay.getDate() + day)
+ const startDay = new Date(targetDay).setHours(0, 0, 0, 0)

Testing

• Tested in Brisbane timezone (GMT+10)
• Events now display in correct day column
• Navigation forward/back preserves correct positioning

🤖 Generated with Claude Code

[huly-github-staging]

Connected to Huly®: UBERF-15325

[domocarroll]

Thank you for the feedback @ArtyomSavchenko. I've cleaned up the PR:

• Force pushed to keep only the calendar fix commit
• Removed all unrelated changes (AI widget, CI workflows, version changes, etc.)

The PR now contains a single commit with just the DayCalendar.svelte fix.

Apologies for the messy initial submission - I'll be more careful to keep PRs focused going forward.

[ArtyomSavchenko]

Thank you for the feedback @ArtyomSavchenko. I've cleaned up the PR:

• Force pushed to keep only the calendar fix commit
• Removed all unrelated changes (AI widget, CI workflows, version changes, etc.)

The PR now contains a single commit with just the DayCalendar.svelte fix.

Apologies for the messy initial submission - I'll be more careful to keep PRs focused going forward.

Thank you again for your contribution and for quickly addressing the feedback.