Add in-app house (villa) purchase + Home picker dialog (RND-1965)

[hugokallstrom]

Summary

Stacked on top of #2947 (vacation home). Adds the SE_HOUSE (villa) form as a sibling to VacationHomeFormDestination inside feature-purchase-house, plus a modal "Home" picker dialog that disambiguates the generic hemforsakring / home-insurance cross-sell.

• HouseFormDestination + HouseFormViewModel in feature-purchase-house/ui/house/. Same form pattern as pet/vacation home (RadioChoiceRow with RadioGroupStyle.Labeled.HorizontalFlow, yesNoOptions() helper, radio values held in ViewModel state with Update* events, text/stepper values in rememberSaveable).
• SubmitHouseFormAndGetOffersUseCase — new use case, reuses the existing HouseShopSessionCreate/HousePriceIntentCreate/HousePriceIntentDataUpdate/HousePriceIntentConfirm Apollo operations (same mutations, different form-data keys).
• HousePurchaseNavGraph.Form branches on productName — SE_VACATION_HOME → VacationHomeFormDestination, SE_HOUSE → HouseFormDestination. Both share the post-form flow (SelectTier → Summary → Signing → Success).
• HomePickerDialog in feature-insurances/insurance/. Modal HedvigDialog with three options: Rental apartment (Hyresrätt), Owned apartment (Bostadsrätt), House (Villa). State held local to the InsuranceGraph navdestination via rememberSaveable.
• Cross-sell URL routing reordered. Specific subpaths now match before the generic hemforsakring / home-insurance rule (which previously silently routed to APARTMENT_RENT). New routes:
  • villaforsakring / home-insurance/house → SE_HOUSE shortcut (no dialog)
  • bostadsratt / home-insurance/homeowner → SE_APARTMENT_BRF (existing)
  • hyresratt / home-insurance/rental → SE_APARTMENT_RENT (existing, slug-narrowed)
  • bare hemforsakring / home-insurance → opens the picker dialog
• No app module changes — onNavigateToHousePurchase(productName) already accepts arbitrary product names from the vacation home PR.

Form fields (v1): street, zipCode, livingSpace, ancillaryArea (biarea), numberCoInsured (stepper 1–5), yearOfConstruction, numberOfBathrooms (stepper 1–10), isSubleted. ssn + email auto-injected from currentMember. extraBuildings: [], currentInsurance: null, useRegistrationAddress: null all sent / omitted in v1.

Design spec: docs/superpowers/specs/2026-05-21-in-app-house-purchase-design.md.
Plan: docs/superpowers/plans/2026-05-21-in-app-house-purchase.md.

Base branch: feat/in-app-vacation-home-purchase. Retarget to develop once #2947 merges.

Test plan

• App builds (./gradlew :app:assemble); Compose previews render for PreviewHouseFormEmpty / Filled / Errors and PreviewHomePickerDialog.
• Generic "Home" cross-sell URL (hemforsakring / home-insurance) opens the HomePickerDialog.
• Tap "House (Villa)" → HouseFormDestination opens.
• Tap "Owned apartment (Bostadsrätt)" → apartment form opens with BRF productName.
• Tap "Rental apartment (Hyresrätt)" → apartment form opens with RENT productName.
• Dialog cancel / scrim-tap / system back dismisses with no navigation.
• Specific URL shortcuts bypass the dialog: hemforsakring/villaforsakring → house form, hemforsakring/bostadsratt → apartment-BRF, hemforsakring/hyresratt → apartment-RENT.
• House form validation: empty street, zipCode < 5 digits, livingSpace 0, year < 1700, missing sublet radio → field-level errors.
• Filling all valid fields → tier select shows SE_HOUSE offer → summary → BankID signing → success → back to insurances.
• Vacation home flow still works (regression check from Add in-app vacation home (fritidshus) purchase flow (RND-1965) #2947).

Out of scope (separate follow-up PRs)

• useRegistrationAddress prefill toggle (needs a member-address query)
• currentInsurance dropdown + insurer query + cancellation flow
• extraBuildings add/remove dialog UI (shared with vacation home)
• SE_APARTMENT_STUDENT (5th hem variant)
• Removing specific URL shortcuts in favor of dialog-only flow

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