Fix pandas 2.0 incompatibility and parameterize load_biome_herarchy_dict

[bleedblack1]

This PR fixes two issues in utils.py.

1. Fix pandas 2.0 incompatibility

Problem:
Series.iteritems() was removed in pandas 2.0, causing an AttributeError.

Fix:
Replaced Series.iteritems() with Series.items() in split_tt().

Additional improvement:
Replaced type(lin) == str with isinstance(lin, str) in split_tt() and i_T().

2. Parameterize load_biome_herarchy_dict()
   Problem:
   load_biome_herarchy_dict() always resolved the biome hierarchy file through
   TaxonomyToVectorParams even when called from other components.

Because the function used an LRU cache, the resolved path was shared across
callers regardless of the pipeline.

Fix:
Added optional parameters:

model_name
model_version

These allow callers to explicitly specify the model repository while keeping
backward-compatible defaults.

resolved issue: #7 #9