refactor(vacay): the invite and share tools read the caller's name from UsersRepository

VacayMcp injected AuthService only to call getCurrentUser for the caller's
username and email before sending an invite or sharing the calendar, which
kept VacayModule importing AuthModule. UsersRepository.findUsernameEmail
answers the same two fields (and undefined for an unknown id, which the
tools already refuse as 'User not found.').

server/scripts/import-boundaries-baseline.json

@@ -16,16 +16,13 @@
     "places -> accommodations",
     "places -> assignments",
     "plugins -> trips",
-    "plugins -> vacay",
     "reservations -> integrations",
     "trip-members -> auth",
     "trip-members -> trips",
     "trip-read-model -> trip-members",
     "trip-read-model -> trips",
     "trips -> trip-members",
-    "trips -> trip-read-model",
-    "trips -> vacay",
-    "vacay -> auth"
+    "trips -> trip-read-model"
   ],
   "sharedImportsDomain": [
     "nest/common/idempotency-cleanup.job.ts -> nest/audit/audit-log.logger.ts",