Refactor loading entries and include baseloader

[DunklesArchipel]

Checklist

• Added an entry in doc/news/.
• Added a test for this change.
• Adapted the documentation for this change.

[Copilot]

Pull request overview

This pull request refactors the entry loading infrastructure by introducing new resource creation functions and incorporating the BaseLoader for handling CSV files with complex structures. The changes improve the API design by separating concerns between resource creation and package building, and enable support for CSV files with multiple header lines.

Changes:

• Refactored CSV loading into separate functions for different resource types (tabular vs. pandas dataframe resources)
• Extracted field updating logic into a standalone update_fields function
• Modified Entry.from_df to work with in-memory pandas resources instead of temporary files
• Added support for CSV files with custom encodings, delimiters, and multiple header lines
• Updated pixi version from v0.50.2 to v0.63.2 across CI workflows

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
unitpackage/local.py	Refactored resource creation functions, added create_tabular_resource_from_csv, create_df_resource_from_csv, create_df_resource_from_df, renamed create_df_resource to create_df_resource_from_tabular_resource, extracted update_fields function, updated create_unitpackage signature
unitpackage/entry.py	Extended from_csv with encoding/delimiter parameters, refactored from_df to use pandas resources, updated mutable_resource property with format validation, modified save method to handle pandas-to-CSV conversion
unitpackage/loaders/baseloader.py	Added documentation example for column_header_lines parameter
pixi.lock	Updated pixi configuration, removed editable flag, added pypi-prerelease-mode option
examples/from_csv/from_csv_multiple_headers.csv	Added test data file with multiple header lines
.github/workflows/*.yml	Updated pixi version to v0.63.2 across all workflows

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[Copilot]

The unspecified_fields list is initialized but never populated. This warning will never be triggered. If the intention is to track fields from the original schema that were not updated with information from the provided fields, the logic should populate this list in the else branch of the main loop (line 339).