Update conda environment

[patrickbrown4]

Summary

This PR updates the conda environment to use new features in gdxpds and geopandas. The main changes are:

• python: 3.11 -> 3.14
• pandas: 2.0 -> 3.0
• gdxpds: 1.4 -> 2.0
• geopandas: 0.14 -> 1.1

Newly added packages are:

• gams.transfer
• highspy

Technical details

Implementation notes

Most of the necessary code changes are related to pandas 3. I've only gotten up to aggregate_regions.py, but most of aggregate_regions.py is removed in #102 and #95, so I'll pick this PR back up once those are merged.

Validation, testing, and comparison report(s)

Checklist for author

Details to double-check

• Charge code provided to reviewers
• Included comparison reports for appropriate test cases
• Documentation updated if necessary
• Code formatting standardized
• Reusable functions used where possible instead of copy/pasted code

General information to guide review

• Zero impact on results of default case
• No large data file(s) added/modified
• No substantive impact on runtime for full-US reference case
• No substantive impact on folder size for full-US reference case
• No change to process flow (runreeds.py, reeds/core/solve/solve.py)
• No change to code organization
• No change to package requirements (environment.yml or Project.toml)

Did you use LLM tools (chatbot or copilot) in the preparation of this PR? If so, describe how

No