feat(features): add bind-dev-seed binders for auth/marketing-pages/navigation/media

Mirrors the canonical blog pattern landed earlier on this branch.

Per feature:
- src/__seeds__/dev.ts — lazy buildDev<Entities>() function using the
  feature's existing factory for sensible defaults
- src/di/bind-dev-seed.ts — bindDevSeed<Feature>() async function that
  rebinds the repo symbol(s) to a populated MockXRepository via
  .toConstantValue
- src/di/bind-dev-seed.test.ts — 3+ tests per feature (populates,
  reachable by id/slug, idempotent)
- package.json — adds ./di/bind-dev-seed subpath export

Tests + use cases continue to construct mocks directly; the seed never
runs from a *.test.ts path. App boot wiring (USE_DEV_SEED env branch)
follows in a separate commit.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/marketing-pages/src/di/bind-dev-seed.ts

@@ -0,0 +1,46 @@
+import { marketingPagesContainer } from "./container.js";
+import { MARKETING_PAGES_SYMBOLS } from "./symbols.js";
+import { MockPagesRepository } from "../infrastructure/repositories/pages.repository.mock.js";
+import { buildDevPages, buildDevSiteSettings } from "../__seeds__/dev.js";
+import type { IPagesRepository } from "../application/repositories/pages.repository.interface.js";
+import type { ISiteSettingsRepository } from "../application/repositories/site-settings.repository.interface.js";
+
+/**
+ * Replace the default empty mocks with populated ones for dev mode + storybook.
+ *
+ * Call this from app boot when `USE_DEV_SEED=true`, mutually exclusive with
+ * `bindProductionMarketingPages(config)`. Tests must NOT call this — they
+ * construct mocks directly and seed via factories per-test.
+ *
+ * Idempotent: safe to call multiple times; each call rebuilds fresh populated
+ * repos and rebinds both symbols.
+ */
+export async function bindDevSeedMarketingPages(): Promise<void> {
+  // Pages repository — MockPagesRepository accepts an initial array.
+  if (marketingPagesContainer.isBound(MARKETING_PAGES_SYMBOLS.IPagesRepository)) {
+    marketingPagesContainer.unbind(MARKETING_PAGES_SYMBOLS.IPagesRepository);
+  }
+
+  marketingPagesContainer
+    .bind<IPagesRepository>(MARKETING_PAGES_SYMBOLS.IPagesRepository)
+    .toConstantValue(new MockPagesRepository(buildDevPages()));
+
+  // Site settings repository — MockSiteSettingsRepository has no mutable
+  // storage so we bind a constant-value implementation directly.
+  if (
+    marketingPagesContainer.isBound(
+      MARKETING_PAGES_SYMBOLS.ISiteSettingsRepository,
+    )
+  ) {
+    marketingPagesContainer.unbind(
+      MARKETING_PAGES_SYMBOLS.ISiteSettingsRepository,
+    );
+  }
+
+  const settings = buildDevSiteSettings();
+  marketingPagesContainer
+    .bind<ISiteSettingsRepository>(MARKETING_PAGES_SYMBOLS.ISiteSettingsRepository)
+    .toConstantValue({
+      getSiteSettings: async () => settings,
+    });
+}