docs(crud): add implementation examples and complete docs task

docs/product-engineering/crud-examples.md

@@ -0,0 +1,69 @@
+# CRUD Examples
+
+## Goal
+
+Provide concrete implementation patterns for new entities adopting `@cms/crud`.
+
+## Example: Service Factory Wiring
+
+```ts
+import { createCrudService } from "@cms/crud"
+import { createPageInputSchema, updatePageInputSchema } from "@cms/content"
+
+const pageCrudService = createCrudService({
+  resource: "page",
+  repository: pageRepository,
+  schemas: {
+    create: createPageInputSchema,
+    update: updatePageInputSchema,
+  },
+  auditHooks: pageAuditHooks,
+})
+```
+
+## Example: Repository Contract
+
+```ts
+const pageRepository = {
+  list: () => db.page.findMany({ orderBy: { updatedAt: "desc" } }),
+  findById: (id: string) => db.page.findUnique({ where: { id } }),
+  create: (input: CreatePageInput) => db.page.create({ data: input }),
+  update: (id: string, input: UpdatePageInput) =>
+    db.page.update({
+      where: { id },
+      data: input,
+    }),
+  delete: (id: string) => db.page.delete({ where: { id } }),
+}
+```
+
+## Example: Action Usage
+
+```ts
+export async function createPage(input: unknown, context?: CrudMutationContext) {
+  return pageCrudService.create(input, context)
+}
+
+export async function updatePage(id: string, input: unknown, context?: CrudMutationContext) {
+  return pageCrudService.update(id, input, context)
+}
+
+export async function deletePage(id: string, context?: CrudMutationContext) {
+  return pageCrudService.delete(id, context)
+}
+```
+
+## Testing Expectations
+
+- validation failure returns `CrudValidationError`
+- missing IDs return `CrudNotFoundError`
+- repository methods are called in expected order
+- audit hooks receive `actor`, `metadata`, `before`, `after`
+
+## Adoption Checklist
+
+1. Add entity schemas in `@cms/content`
+2. Add repository + service in `@cms/db`
+3. Add unit tests for contract + validation
+4. Wire route/action permission checks before mutations
+5. Add docs links and TODO updates