Product bundles add-on (spec 0085)

[glennjacobs]

Summary

Implements spec 0085: a new first-party lunarphp/bundles package that sells a set of product variants as one product, plus the two small core seams it needs.

• Core (slices 1-2): order_lines.parent_line_id with OrderLine::parent()/components()/isComponent() and a topLevel scope; the creation stages skip component lines; refundableQuantity() is 0 for components; ProductVariant::getTotalInventory()/canBeFulfilledAtQuantity() now delegate to a new ResolvesInventory action contract (VariantInventory DTO), bound in ActionServiceProvider. Additive; no contract signatures change. The order_lines baseline migration is edited in place (v2 alpha rule).
• Panel first party (slice 6): component lines nest under their parent in the order view and pick lists ("Part of ..."), the refund composer and "Other items" list top-level lines only; Section is exported from @lunarphp/panel.
• packages/bundles (slices 3-5): Bundle/BundleGroup/BundleComponent on a variant; fixed and configurable bundles; fixed or components pricing with materialised price rows and repricing listeners plus lunar:bundles:reprice; derived stock through a decorator on ResolvesInventory; cart-line selection validator and a cart_lines pricing stage; an order-creation stage that gives every bundle line zero-priced component lines so fulfilment and stock commitment work unchanged.
• Panel add-on (slices 7-8): a SectionExtension on Catalog with the bundle editor on the product and variant pages, an "Included in bundles" sidebar card, a Bundle badge column and "Bundles only" filter on the products table, 16 locales.
• Demo data (slice 9): two bundles seeded when the package is installed.

Docs PR: lunarphp/docs docs/product-bundles (opened alongside this one).

Notes for review

• No third-party dependency is added; composer.json changes are the sub-package wiring and a suggest on demo-data.
• Deviations from the spec are recorded in the spec's implementation plan (always-visible badge column, the extra GET bundles/products/{product} route, a cart_lines pipeline stage instead of a cart-line modifier because core never invokes calculating()).
• Pre-existing, not fixed here: OrderLineQuantity::validate() lazy loads $orderLine->order, which trips preventLazyLoading on an orderIdToUpdate re-run that changes a line quantity.
• Open questions from the spec (mixed-rate tax, the inventory card on a bundle variant, per-component refunds, queued repricing) are unchanged.

Test plan

• vendor/bin/pest --testsuite core --parallel (1291 passed)
• vendor/bin/pest --testsuite panel --parallel (937 passed)
• vendor/bin/pest --testsuite bundles --parallel (71 passed)
• vendor/bin/pest --testsuite demo-data --parallel (34 passed)
• vendor/bin/phpstan analyse --no-progress --memory-limit=2G
• vendor/bin/pint --dirty
• panel npm run type-check, npm test; add-on and panel bundles rebuilt
• translation completeness script: 0 missing, 0 stale

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