Migrate spatial code from sp/rgeos to sf

We are migrating the spatial codebase from the legacy sp/rgeos stack to the sf package.
This is motivated by the deprecation of rgeos and the recommendation to use sf for vector data handling in R

Scope:

• Remove remaining rgeos dependencies and replace them with sf equivalents
• Gradually phase out sp usage where feasible, while keeping sp temporarily available if needed
• Ensure all new spatial developments use sf only

Tasks:

• Replace all rgeos calls (e.g. distance and centroid functions) with the corresponding sf functions
• Convert Spatial* objects loaded from files to sf objects early in the workflow
• Replace @data access patterns with sf/data.frame access ($, [[ ]])
• Run the app and scripts to confirm there are no runtime errors related to spatial operations and that behaviour remains unchanged from a user point of view