NMS-Belize/surface

AI Summary: Refactor the database schema to improve data integrity and querying efficiency. This involves converting several CharFields in the `stations` model (and potentially others) representing categorical metadata into ForeignKey relationships with newly created models for each category (e.g., Observer, Organization, Zone). This requires identifying the relevant fields, creating new Django models, migrating existing data, updating forms, views, and serializers, and handling any resulting errors.