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

Per Plan 9 (spec R1-R28):
- Use cases: input + output schemas (signIn, signUp); input-only for
  signOut (void output). Use case body validates output via
  outputSchema.parse before returning.
- Controllers: receive `unknown`; safeParse with the use-case schema;
  presenter (returning cookie) for signIn/signUp; void return for
  signOut.
- New integrations/api/procedures.ts with authProcedure built via
  defineErrorMiddleware([[InputParseError,"BAD_REQUEST"],
  [AuthenticationError,"UNAUTHORIZED"], [UnauthenticatedError,
  "UNAUTHORIZED"], [UnauthorizedError,"FORBIDDEN"]]).
- Router uses authProcedure + .input(xInputSchema) for every procedure.
- src/index.ts exports schemas + types + IUseCase/IController aliases.
- package.json gains ./ui subpath; src/ui/index.ts placeholder
  (auth has no query builders today).
- New tests: R25 output-validation per use case (signIn, signUp);
  R26 router error-mapping (UNAUTHORIZED on missing user,
  BAD_REQUEST on schema fail).

Refactor log: §1, §2, §3.1, §3.2, §3.3, §5.1, §5.2, §6.1, §6.2
Spec: R1–R6, R8–R15, R18, R19, R22–R26

packages/auth/src/application/use-cases/sign-in.use-case.ts

@@ -1,25 +1,37 @@
+import { z } from "zod";
+
 import { AuthenticationError } from "../../entities/errors/auth";
-import type { Cookie } from "../../entities/models/cookie";
-import type { Session } from "../../entities/models/session";
+import { cookieSchema } from "../../entities/models/cookie";
+import { sessionSchema } from "../../entities/models/session";
 import type { IUsersRepository } from "../repositories/users.repository.interface";
 import type { IAuthenticationService } from "../services/authentication.service.interface";
 
+// ── Input ────────────────────────────────────────────────────────────────
+export const signInInputSchema = z
+  .object({
+    username: z.string().min(3).max(31),
+    password: z.string().min(6).max(255),
+  })
+  .strict();
+export type SignInInput = z.infer<typeof signInInputSchema>;
+
+// ── Output ───────────────────────────────────────────────────────────────
+export const signInOutputSchema = z.object({
+  session: sessionSchema,
+  cookie: cookieSchema,
+});
+export type SignInOutput = z.infer<typeof signInOutputSchema>;
+
+// ── Use case ─────────────────────────────────────────────────────────────
 export type ISignInUseCase = ReturnType<typeof signInUseCase>;
 
 export const signInUseCase =
-  (
-    usersRepository: IUsersRepository,
-    authenticationService: IAuthenticationService,
-  ) =>
-  async (input: {
-    username: string;
-    password: string;
-  }): Promise<{ session: Session; cookie: Cookie }> => {
+  (usersRepository: IUsersRepository, authenticationService: IAuthenticationService) =>
+  async (input: SignInInput): Promise<SignInOutput> => {
     const existingUser = await usersRepository.getUserByUsername(input.username);
     if (!existingUser) {
       throw new AuthenticationError("User does not exist");
     }
-
     const validPassword = await authenticationService.verifyPassword(
       existingUser.passwordHash,
       input.password,
@@ -27,6 +39,6 @@ export const signInUseCase =
     if (!validPassword) {
       throw new AuthenticationError("Incorrect username or password");
     }
-
-    return await authenticationService.createSession(existingUser);
+    const result = await authenticationService.createSession(existingUser);
+    return signInOutputSchema.parse(result);
   };