build: align declared pydantic floor with FastAPI 0.136 transitive requirement

FastAPI 0.136 raises its minimum pydantic requirement to >=2.9.0. Our
declared pin was still >=2.4.0,<2.10.0 — Poetry's solver enforced the
effective floor via the lock, but the declared metadata was misleading
and an unlocked install could surface confusing resolution attempts.

Update the explicit pin to >=2.9.0,<2.10.0 so the metadata reflects
reality. No runtime change; resolved version remains 2.9.2.

Author: yyyyyyyan

poetry.lock

@@ -41,7 +41,7 @@ dependencies = [
     "sqlalchemy-celery-beat (>=0.8.4,<0.9.0)",
     "aioresponses (>=0.7.7,<0.8.0)",
     "itsdangerous (>=2.1.2,<3.0.0)",
-    "pydantic (>=2.4.0,<2.10.0)",
+    "pydantic (>=2.9.0,<2.10.0)",
     "pyyaml (>=6.0.1,<7.0.0)",
     "python-nomad (>=2.0.0,<3.0.0)",
     "sqlalchemy (>=2.0.34,<3.0.0)",