Fix various warnings and deprecations (#23641)

* Migrate to fastapi lifespan for startup events

The `on_event` style decorator is deprecated

https://fastapi.tiangolo.com/advanced/events/

* Migrate to pydantic TypeAdapter

https://pydantic.dev/docs/validation/2.12/get-started/migration/#introduction-of-typeadapter

* Replace pytz with native tz-aware objects and zoneinfo library

Supported from Python 3.9, see https://peps.python.org/pep-0615/. Also
https://blog.ganssle.io/articles/2019/11/utcnow.html.

Also provide tzdata as new dependency to supplement systems without local
tzdata information.

* Provide lookup for normalized timezone names

This provides a helper to look up the correct timezone name independent
of the casing of the given timezone name.

* Test timezone naming normalization and error handling

docker/main/requirements-wheels.txt

@@ -25,7 +25,7 @@ peewee_migrate == 2.3.*
 psutil == 7.2.*
 pydantic == 2.13.*
 git+https://github.com/fbcotter/py3nvml#egg=py3nvml
-pytz == 2026.*
+tzdata == 2026.5
 pyzmq == 27.2.*
 ruamel.yaml == 0.19.*
 tzlocal == 5.4.4