Overhaul `predict_map` Function for Compatibility with Updated Policy Workflow

[Paul-Carvalho]

Body:

This issue is for a general update ("overhaul") of the predict_map function in the FishSET R package. This work should proceed after the completion of the run_policy overhaul, as predict_map depends on upstream changes.

Scope and Tasks:

• Refactor and update the predict_map function for compatibility with the newly overhauled run_policy and its revised interface/outputs.
• Update any additional helper functions or files directly supporting predict_map as needed.
• Review and revise function logic to take advantage of efficiency or clarity improvements from the new fishset_design and fishset_fit functions and coding standards (see FishSET Wiki).
• Audit and update code formatting, structure, and variable naming for clarity and maintainability.
• Add or update unit tests to provide coverage for all main code paths in predict_map and its helpers.
• Document any breaking changes to the function's interface, expected outputs, or downstream dependencies (such as the Shiny interface).

Notes:

• This work should be started only after the run_policy overhaul issue is completed and merged.
• If additional downstream modules (e.g., Shiny UI/server components) need to be updated for compatibility with predict_map, document and address them in future issues.
• The new FishSET coding standards and models are detailed in the repo Wiki.
• If significant pain points, performance issues, or sources of confusion are encountered, comment here and/or consider splitting into additional targeted issues.

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This overhaul will ensure continued compatibility, code quality, and maintainability for the next generation of FishSET development.