feat(auth)!: migrate customer metadata auth

Remove local auth and user-management endpoints in favor of Keycloak-backed metadata users, project context, admin metadata APIs, and agent auth context.

app/auth/project_dependencies.py

@@ -25,6 +25,7 @@ logger = logging.getLogger(__name__)
 @dataclass(frozen=True)
 class ProjectContext:
     project_id: UUID
+    project_code: str
     user_id: UUID
     project_role: str
 
@@ -85,6 +86,7 @@ async def get_project_context(
 
     return ProjectContext(
         project_id=project.id,
+        project_code=project.code,
         user_id=user.id,
         project_role=membership_role,
     )