[scheduler] Timezone Issue 8: show in the recurrence tab the data converted to UI timezone

[rita-codes]

DO NOT merge, merge after #20744

Recurrence rules are now displayed in the user's display timezone in the recurrence tab, so the weekdays shown in the UI match what the user actually sees on the calendar.

When the user edits a recurrence rule, the changes are projected back to the event data timezone before being persisted, ensuring internal consistency.

WEEKLY BYDAY rules

• Are projected from the event data timezone to the display timezone for rendering.
• When edited, they are converted back from display timezone to data timezone using the event start as an anchor.
• This ensures round-trip consistency between what the user sees and what is stored.

MONTHLY BYDAY rules with ordinals (e.g. 1MO, -1FR)

• Are intentionally not projected. Ordinals represent a calendar position in the event's data timezone and do not map to a stable or reliable representation in another timezone.
• When edited, the rule is preserved exactly as entered by the user.

UNTIL, start, end, and exception dates are converted back to the data timezone on update.

• I have followed (at least) the PR section of the contributing guide.

[mui-bot]

Deploy preview: https://deploy-preview-20769--material-ui-x.netlify.app/

Bundle size report

Bundle	Parsed size	Gzip size
@mui/x-data-grid	0B(0.00%)	0B(0.00%)
@mui/x-data-grid-pro	0B(0.00%)	0B(0.00%)
@mui/x-data-grid-premium	0B(0.00%)	0B(0.00%)
@mui/x-charts	0B(0.00%)	0B(0.00%)
@mui/x-charts-pro	0B(0.00%)	0B(0.00%)
@mui/x-charts-premium	0B(0.00%)	0B(0.00%)
@mui/x-date-pickers	0B(0.00%)	0B(0.00%)
@mui/x-date-pickers-pro	0B(0.00%)	0B(0.00%)
@mui/x-tree-view	0B(0.00%)	0B(0.00%)
@mui/x-tree-view-pro	0B(0.00%)	0B(0.00%)

Details of bundle changes

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