[Analytics Hub] Connect data and UI for Sessions analytics card

[rachelmcr]

Closes: #8365

Description

This PR connects the data used for the sessions card (current period order stats and site summary stats) with the card UI.

For now, this will display placeholders and a sync error because we aren't fetching real data yet. The data will be fetched in another PR.

Changes

• Adds a siteStats property to store the fetched SiteSummaryStats (currently always nil).
• Adds a helper that returns a AnalyticsReportCardCurrentPeriodViewModel for the sessions card.
• Localizes the card strings.

Testing

1. Build and run the app.
2. Tap "See more" to open the Analytics Hub.
3. Confirm the Sessions card displays real data (placeholders and sync error for now).

Screenshots

Submitter Checklist

Update release notes:

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

[peril-woocommerce]

	Warnings
⚠️	This PR is assigned to a milestone which is closing in less than 2 days Please, make sure to get it merged by then or assign it to a later expiring milestone

Generated by 🚫 dangerJS

[wpmobilebot]

You can test the changes from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr8409-03ebb79 on your iPhone

If you need access to App Center, please ask a maintainer to add you.

[rachelmcr]

@ealeksandrov I see you're reviewing this, and just wanted to give you a heads up that I'd forgotten to bind the data to the card VM in bindViewModelsWithData(). I've just merged the latest from trunk and added that binding, which should make these changes complete.

[ealeksandrov]

LGTM!