Guided package builder for configurable hour bundles

What changed

Hourly package templates can now be configured as guided public offers instead of only static bundles. Studios define the allowed hour options, service plans, optional bundled add-ons, and the default package combination in admin.

On the public `/packages` page, buyers now get a package builder that previews the selected combination before checkout. The final package price is derived server-side, and Stripe fulfillment stores the chosen hours, service plan, and bundled add-ons in the existing wallet grant flow.

Why this matters

• Studios can merchandise flexible package offers without exposing an open-ended custom quote flow.
• Buyers see one clear final package price while still being able to choose from the combinations the studio actually wants to sell.
• Service-plan-specific packages and bundled extras stay attached to the purchased entitlement instead of relying on manual admin follow-up.
• Public package sales remain separate from booking checkout, so prepaid package logic stays cleaner for accounting and later redemption.