Bookings: Fetch and display assigned staff on booking details

[itsmeichigo]

Closes WOOMOB-1522

Description

This PR supports fetching and displaying assigned staff on booking details:

• Adds readonly model for BookingResource.
• Integrates /bookings/v2/resources/{id} endpoint
• Adds CoreData entity for BookingResource to cache results.
• Updates BookingAction and BookingStore to fetch resources.
• Updates booking details view to fetch and display resources. Due to the time shortage, I could not polish the UI with proper loading state, so for now the Assigned Staff row shows only "-" while fetching is in progress.

Testing steps

1. Log in to a CIAB store with existing bookings.
2. Navigate to the Bookings tab and select a booking with associated order.
3. Confirm that after a few seconds the assigned staff value is displayed.
4. Navigate back out and in again to the same booking detail screen.
5. Confirm that the assigned staff value is available immediately as it was cached from the last fetch.

Testing information

• Tested with simulator iPhone 17.
• Added unit tests.

Screenshots

Simulator.Screen.Recording.-.iPhone.17.-.2025-10-16.at.17.43.57.mov

---

• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[dangermattic]

	2 Warnings
⚠️	This PR is larger than 300 lines of changes. Please consider splitting it into smaller PRs for easier and faster reviews.
⚠️	This PR is assigned to the milestone 23.5. This milestone is due in less than 2 days. Please make sure to get it merged by then or assign it to a milestone with a later deadline.

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[wpmobilebot]

📲 You can test the changes from this Pull Request in WooCommerce iOS Prototype by scanning the QR code below to install the corresponding build.

	App Name	WooCommerce iOS Prototype
	Build Number	pr16249-0c2def2
	Version	23.4
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	0c2def2
	Installation URL	111qebbg7houo

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[adborbas]

Good job 👍