deploy follow fixes

[KascadeKyle]

Summary

This PR strengthens validation in deployable_follow to prevent invalid or client-manipulated move requests.

Changes

• Added proximity sanity check (MAX_PROXIMITY_DISTANCE)

  • Rather than just checking if mobile_state exists for the deployable, fetch the coordinates and use it in our validation.
  • Require the following to all be in the same dimension and within a bounded distance of each other:
    • Player location (server)
    • Deployable location (server)
    • Client-provided origin
    • Client-provided destination
  • Helps prevent client coordinate spoofing or inconsistent move requests.

• Fixed water-depth validation logic

  • Previously rejected only when both start and target were invalid (&&).
  • This allowed moves where one endpoint was invalid (e.g., land → water or water → land).
  • Now ensures start, target, and the deployable’s authoritative location all satisfy pathfinding water-depth constraints.

• Removed misleading copied comment

  • Removed the comment:

    // Validate Boat Move. Note that this for the short term, ideally at some point
    // we will re-enable the above _validate_move that has more comprehensive checks

  • This comment was copied from BitCraftServer\packages\game\src\game\handlers\player\deployable_move.rs and was misleading here (the reducer does not deal with boats).