fix: refresh slots when timezone changes with restriction schedule

[Vipeen-Kumar]

What does this PR do?

Fixes an issue where available time slots were not refreshed when the user changed the timezone for events that use a restriction schedule.

Previously, changing the timezone updated the UI timezone but did not invalidate and refetch the schedule data, causing stale or incorrect slots to be displayed. This PR ensures the schedule is invalidated and refetched when the timezone changes, only when useBookerTimezone is enabled and a restriction schedule is present, avoiding unnecessary network requests.

• Fixes Upon changing timezone, we need to update slots when restrictionSchedule is being used with useBookerTimezone enabled #22319
• Fixes CAL-6060

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Visual Demo

Before

• Changing the timezone does not update available slots
• Slots remain based on the previous timezone

After

• Changing the timezone immediately refreshes available slots
• Slots correctly reflect the selected timezone

(Screenshots / video can be added if required)

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Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code
• This change does not require documentation updates (N/A)
• I confirm the fix works as expected through manual testing

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How should this be tested?

1. Open a public booking page for an event with a restriction schedule
2. Ensure useBookerTimezone is enabled for the event
3. Navigate to the booking page
4. Change the timezone using the timezone selector
5. ✅ Verify that available slots update immediately and reflect the new timezone
6. Repeat with different timezones to confirm consistent behavior

Expected Result

• Slots refresh correctly on timezone change
• No unnecessary refetches when timezone does not change
• No regression for events without restriction schedules

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Checklist

• Read the contributing guide
• Code follows existing project patterns
• No new warnings introduced

[CLAassistant]

All committers have signed the CLA.

[cubic-dev-ai]

No issues found across 2 files