refactor(marketing-pages): unify use-case I/O schemas + presenter + feature error map

Per Plan 9 (spec R1-R28):
- Use cases: input + output schemas (getPageBySlug, getSiteSettings).
  Site-settings input is z.object({}).strict() per R5 (uniform input).
- Controllers: unknown input + identity presenter; void output not
  applicable (both use cases return data).
- New integrations/api/procedures.ts with marketingPagesProcedure
  ([InputParseError → BAD_REQUEST], [PageNotFoundError → NOT_FOUND]).
- Router uses marketingPagesProcedure + .input(xInputSchema).
- src/index.ts: remove pageBySlugQuery/siteSettingsQuery; export
  schemas + types + IUseCase/IController aliases.
- src/ui/index.ts (NEW); package.json adds ./ui subpath.
- R25 output-validation tests + R26 router error-mapping test.

Refactor log: §1, §2, §3.1, §3.2, §3.3, §5.1, §5.2, §6.1, §6.2
Spec: R1–R6, R8–R15, R18–R20, R22–R26

packages/marketing-pages/src/interface-adapters/controllers/get-site-settings.controller.ts

@@ -1,10 +1,23 @@
-import type { SiteSettings } from "../../entities/models/site-settings";
-import type { IGetSiteSettingsUseCase } from "../../application/use-cases/get-site-settings.use-case";
+import { InputParseError } from "../../entities/errors/common";
+import {
+  getSiteSettingsInputSchema,
+  type GetSiteSettingsOutput,
+  type IGetSiteSettingsUseCase,
+} from "../../application/use-cases/get-site-settings.use-case";
+
+function presenter(value: GetSiteSettingsOutput) {
+  return value;
+}
 
 export type IGetSiteSettingsController = ReturnType<typeof getSiteSettingsController>;
 
 export const getSiteSettingsController =
   (getSiteSettingsUseCase: IGetSiteSettingsUseCase) =>
-  async (): Promise<SiteSettings> => {
-    return getSiteSettingsUseCase();
+  async (input: unknown): Promise<ReturnType<typeof presenter>> => {
+    const parsed = getSiteSettingsInputSchema.safeParse(input);
+    if (!parsed.success) {
+      throw new InputParseError("Invalid get-site-settings input", { cause: parsed.error });
+    }
+    const result = await getSiteSettingsUseCase(parsed.data);
+    return presenter(result);
   };