Pydantic validation for the v1.2 API

[Yannicked]

This PR introduces a @pydantic_validate decorator that wires up typed request/response handling for all v1.2 API endpoints, replacing the previous mix of manual jsonify, try/except DatabaseError, and ad-hoc error returns.

This also automatically adds the expected request and response data to the autogenerated swagger API docs:

[deepakmaroo]

There is exception when Dashboard request for list of simulations

127.0.0.1 - - [13/Mar/2026 09:50:27] "OPTIONS /v1.2/simulations?code.name=&status=&uploaded_by= HTTP/1.1" 200 -
Unhandled exception in SimulationList.get
Traceback (most recent call last):
  File "/home/ITER/marood/Desktop/redhat-workspace/testing/SimDB_Test/src/simdb/remote/core/pydantic_utils.py", line 287, in wrapper
    result = f(*args, **kwargs)
             ^^^^^^^^^^^^^^^^^^
  File "/home/ITER/marood/Desktop/redhat-workspace/testing/SimDB_Test/src/simdb/remote/apis/v1_2/simulations.py", line 206, in get
    return PaginatedResponse[SimulationListItem].model_validate(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ITER/marood/Desktop/redhat-workspace/testing/SimDB_Test/venv/lib/python3.11/site-packages/pydantic/main.py", line 716, in model_validate
    return cls.__pydantic_validator__.validate_python(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
pydantic_core._pydantic_core.ValidationError: 1 validation error for PaginatedResponse[SimulationListItem]
count
  Input should be a valid integer, got a number with a fractional part [type=int_from_float, input_value=110.66666666666667, input_type=float]
    For further information visit https://errors.pydantic.dev/2.12/v/int_from_float
127.0.0.1 - - [13/Mar/2026 09:50:27] "GET /v1.2/simulations?code.name=&status=&uploaded_by= HTTP/1.1" 500 -

No sure if below error occurred due to local database migration applied

(venv) [marood@98dci4-srv-1002 SimDB_Test]$ simdb --debug remote sdcc list -l 10
Error: Corrupted data - non-optional metadata is None.
Traceback (most recent call last):
  File "/home/ITER/marood/Desktop/redhat-workspace/testing/SimDB_Test/venv/bin/simdb", line 10, in <module>
    sys.exit(main())

  File "/home/ITER/marood/Desktop/redhat-workspace/testing/SimDB_Test/src/simdb/cli/remote_api.py", line 584, in list_simulations
    return [Simulation.from_data(sim) for sim in data["results"]]
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ITER/marood/Desktop/redhat-workspace/testing/SimDB_Test/src/simdb/cli/remote_api.py", line 584, in <listcomp>
    return [Simulation.from_data(sim) for sim in data["results"]]
            ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ITER/marood/Desktop/redhat-workspace/testing/SimDB_Test/src/simdb/database/models/simulation.py", line 340, in from_data
    metadata = checked_get(data, "metadata", list)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ITER/marood/Desktop/redhat-workspace/testing/SimDB_Test/src/simdb/database/models/utils.py", line 69, in checked_get
    raise ValueError(f"Corrupted data - non-optional {key} is None.")
ValueError: Corrupted data - non-optional metadata is None.