Closes #1792

Changes proposed in this Pull Request

• Fixes a bug where carrier colors were not updated in the balance map plotting script after a config change post solving a network.

• Ensures tech_colors are now read directly from the Snakemake config at runtime for the balance map.

• This brings consistency with all the other plotting functions e.g. plot_balance_timeseries

• Modified scripts/plot_balance_map.py to fetch tech_colors from current config.

Checklist

• [✔️ ] I tested my contribution locally and it works as intended.
• [✔️ ] Code and workflow changes are sufficiently documented.
• [ ❌] Changed dependencies are added to envs/environment.yaml.
• [❌ ] Changes in configuration options are added in config/config.default.yaml.
• [❌ ] Changes in configuration options are documented in doc/configtables/*.csv.
• [❌ ] Sources of newly added data are documented in doc/data_sources.rst.
• [❌] A release note doc/release_notes.rst is added.