feat(auth): migrate anonymous consent on signUp when cc_consent cookie present

Adds ConsentFactoryProtocol / ConsentGrantMeta / ConsentProtocol to
core-shared/di/bind-protocols so feature binders can wire per-user
consent without a hard dep on the optional @repo/core-consent package.
BindContext gains an optional consentFactory? field following the same
pattern as bus?, auditLog?, etc.

signUpUseCase gains a 4th optional dep (consentFactory). When present
and the input includes a cookieHeader containing cc_consent=<categories>,
the use case calls consent.grant for each category with
method:"signup-migration" and returns a clearCookie payload (Max-Age:0)
so the anonymous cookie is cleared on the HTTP response.

Tests use RecordingConsent from @repo/core-testing to assert migration
call shape and cookie-clear; no-cookie and no-factory branches are also
covered. All coverage bands hold at 100% for use-cases.

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

packages/auth/tests/sign-in-flow.feature.test.ts

@@ -19,7 +19,9 @@ describe("auth feature: sign-up → sign-in → sign-out", () => {
     const auth = new MockAuthenticationService(users);
 
     const signIn = signInController(signInUseCase(users, auth));
-    const signUp = signUpController(signUpUseCase(users, auth, new RecordingEventBus()));
+    const signUp = signUpController(
+      signUpUseCase(users, auth, new RecordingEventBus(), undefined),
+    );
     const signOut = signOutController(signOutUseCase(auth));
 
     // signUp returns a cookie (presenter shape)