feat(core-consent): add handlers and consentRouter tRPC router

Protocol-agnostic handlers (grant, withdraw, isGranted, getCategories)
in core-consent/handlers/ call IConsent methods and return typed results.

consentRouter uses a consent-specific tRPC context (userId + consentFactory)
so each procedure can resolve the per-user IConsent instance at call time.
Auth middleware guards all four procedures and maps UnauthenticatedError →
UNAUTHORIZED via defineErrorMiddleware from core-shared (no local duplicate).

76 tests passing; new handler and router code at 100% branch coverage.

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

packages/core-consent/src/entities/errors/consent.ts

@@ -0,0 +1,7 @@
+export class UnauthenticatedError extends Error {
+  constructor(message = "Not authenticated") {
+    super(message);
+    this.name = "UnauthenticatedError";
+    Object.setPrototypeOf(this, UnauthenticatedError.prototype);
+  }
+}