`OptimizationConfig.seed` is `PositiveInt` — `seed=0` is rejected while `Pipeline(seed=0)` accepts it

What happens

OptimizationConfig.seed is declared PositiveInt (_optimization_config.py:52), so seed=0 — a perfectly normal seed, and the first value of any seed grid — is rejected:

>>> from autointent import OptimizationConfig
>>> OptimizationConfig(seed=0, search_space=[])
ValidationError: 1 validation error for OptimizationConfig
seed
  Input should be greater than 0 [type=greater_than, input_value=0, input_type=int]

It is inconsistent with the rest of the API: Pipeline(seed=...) and Pipeline.from_search_space(seed=...) take int | None (_pipeline.py:54, :111) and accept 0, while Pipeline.from_preset(name, seed=0) and Pipeline.from_optimization_config fail because they build an OptimizationConfig (:124-127).

Proposed

NonNegativeInt (or plain int, matching Pipeline). Darinochka/AutoIntent-experiments#43 works around it by building the pipeline with the default seed and setting pipeline._seed = 0 afterwards.

Follow-up from #350.

Read src/autointent/_optimization_config.py at line 52 and compare its seed type with the seed parameters in src/autointent/_pipeline/_pipeline.py at lines 54, 111, and 124-127. Verify the public constructors accept seed=0 consistently, including OptimizationConfig, Pipeline.from_preset, and Pipeline.from_optimization_config.