feat(sellers): typed domain models for future Seller Management - no logic, no API, no auth changes

Typed models only, per mission. Nothing outside the new files reads
or writes any of this yet.

New core/sellers/models/ (mirrors core/products/models,
core/auth/models convention):
- MarketplaceRef - minimal {id,slug,name} reference from a seller
  back to its marketplace, distinct from bootstrap's TenantConfig.
- SellerStatus - 'pending'|'active'|'suspended'|'disabled', no
  transition logic.
- SellerScope - {sellerId, marketplaceId}, domain-level counterpart
  to BootstrapConfig.seller (SellerConfig from the ADR-011 pass).
- SellerBranding (+SellerContact/SellerAddress/SellerThemeOverrides)
  - logo/banner/description/contacts/address/theme overrides, every
    field optional. Marketplace branding/theme remain default;
    nothing consumes this yet.
- SellerPermissionRole/SellerPermissions - marketplaceOwner/seller/
  sellerStaff/platformAdmin. Separate vocabulary from the existing
  AdminRole (core/auth/models/permission.model.ts) - not merged, not
  wired into any guard, zero auth behavior change.
- Seller - the eventual entity, composed from the above.

Changed (optional-only, verified backward compatible):
- Item (models/item.model.ts) gained sellerId?: string
- AdminProduct (features/admin/products/models/) gained
  sellerId?: string
- AdminOrder (features/admin/orders/models/) gained sellerId?: string

Absent means marketplace-owned in every case, exactly like every
existing product/order today. No consumer of any of these three
models needed updating. AdminOrderItem (per-line-item ownership) and
the existing PermissionsConfig/AdminRole system were deliberately not
touched - out of scope for this pass.

Added docs/architecture/foundation/Seller-Management-Domain-Models.md
documenting every new type, every changed field, and the explicit
non-goals list. Linked from the foundation README alongside ADR-011
and the diagrams doc.

tsc --noEmit clean, arch:check (boundaries + cycles) clean.

src/app/core/sellers/models/index.ts

@@ -0,0 +1,6 @@
+export * from './marketplace-ref.model';
+export * from './seller-branding.model';
+export * from './seller-permissions.model';
+export * from './seller-scope.model';
+export * from './seller-status.model';
+export * from './seller.model';

src/app/core/sellers/models/marketplace-ref.model.ts

@@ -0,0 +1,14 @@
+import { UUID } from '../../../shared/types/primitive.types';
+
+/**
+ * Minimal marketplace reference as seen from a Seller record - not the full
+ * runtime `TenantConfig` (shared/models/config/tenant.model.ts), which stays
+ * the bootstrap-time source of truth for the active marketplace (ADR-001).
+ * This is just enough to say "this seller belongs to that marketplace"
+ * without pulling in the whole tenant contract.
+ */
+export interface MarketplaceRef {
+  id: UUID;
+  slug: string;
+  name: string;
+}

src/app/core/sellers/models/seller-branding.model.ts

@@ -0,0 +1,34 @@
+/**
+ * Future per-seller branding overrides - all optional. Absent fields fall
+ * back to marketplace branding (shared/models/config/branding.model.ts,
+ * BrandingConfig) and marketplace theme (theme.model.ts, ThemeConfig).
+ * Marketplace branding remains the default in every case; nothing here is
+ * consumed anywhere yet.
+ */
+export interface SellerContact {
+  email?: string;
+  phone?: string;
+}
+
+export interface SellerAddress {
+  line1?: string;
+  line2?: string;
+  city?: string;
+  region?: string;
+  postalCode?: string;
+  country?: string;
+}
+
+export interface SellerThemeOverrides {
+  primaryColor?: string;
+  accentColor?: string;
+}
+
+export interface SellerBranding {
+  logoUrl?: string;
+  bannerUrl?: string;
+  description?: string;
+  contacts?: SellerContact;
+  address?: SellerAddress;
+  themeOverrides?: SellerThemeOverrides;
+}

src/app/core/sellers/models/seller-permissions.model.ts

@@ -0,0 +1,16 @@
+/**
+ * Future permission roles for the Seller Management module - a separate
+ * vocabulary from the existing platform admin roles (core/auth/models/
+ * permission.model.ts, AdminRole: Owner/Manager/Support/ReadOnly). No
+ * authentication or authorization change is introduced by this file; these
+ * types are unused until Seller Management is actually implemented.
+ */
+export type SellerPermissionRole =
+  | 'marketplaceOwner'
+  | 'seller'
+  | 'sellerStaff'
+  | 'platformAdmin';
+
+export interface SellerPermissions {
+  role: SellerPermissionRole;
+}

src/app/core/sellers/models/seller-scope.model.ts

@@ -0,0 +1,14 @@
+import { UUID } from '../../../shared/types/primitive.types';
+
+/**
+ * Resolved seller-scoped request context - the domain-level counterpart to
+ * `BootstrapConfig.seller` (`SellerConfig`, shared/models/config/seller.model.ts).
+ * That type is the bootstrap wire shape; this one is what seller-aware
+ * domain code (products, orders, permissions) references once it exists.
+ * Backend-resolved only, same as tenant resolution (ADR-001, ADR-011) - no
+ * frontend code constructs this itself.
+ */
+export interface SellerScope {
+  sellerId: UUID;
+  marketplaceId: UUID;
+}

src/app/core/sellers/models/seller-status.model.ts

@@ -0,0 +1,6 @@
+/**
+ * Lifecycle status of a seller record. No transition logic exists yet - this
+ * is the typed vocabulary only, for future Seller Management CRUD/moderation
+ * to build against.
+ */
+export type SellerStatus = 'pending' | 'active' | 'suspended' | 'disabled';

src/app/core/sellers/models/seller.model.ts

@@ -0,0 +1,20 @@
+import { ISODateTime, UUID } from '../../../shared/types/primitive.types';
+import { MarketplaceRef } from './marketplace-ref.model';
+import { SellerBranding } from './seller-branding.model';
+import { SellerStatus } from './seller-status.model';
+
+/**
+ * A seller record - the future entity Seller Management CRUD will operate
+ * on. No repository, gateway, or facade exists yet; this is the typed shape
+ * only, so future work has a settled model instead of inventing one ad hoc.
+ */
+export interface Seller {
+  id: UUID;
+  marketplace: MarketplaceRef;
+  name: string;
+  slug: string;
+  status: SellerStatus;
+  branding?: SellerBranding;
+  createdAt: ISODateTime;
+  updatedAt: ISODateTime;
+}