Add an in-game ship navigation screen and autopilot

[frostdev-ops]

Why

Ship crews currently need external coordinate knowledge and computer scripts to plan multi-leg travel. This adds an in-game navigation screen with server-authoritative route validation and autopilot control.

Scope

• Adds the navigation GUI, map, destinations, route previews, and autopilot modes.
• Adds packet IDs 8/9 and 103 with permission and action validation on the server.
• Persists backward-compatible navigation state and adds strict destination handling to jumps.
• Includes only the scan/snapshot helpers and math accessors required by navigation.

Excluded: chunk batching, air scheduling, global-region indexes, stale tile-entity guards, offline avatars, jump NBT changes, controller persistence fixes, and release metadata.

Evidence

• Java 8 offline Gradle build: passed (test NO-SOURCE).
• Merges cleanly with each of the five replacement branches.
• Navigation-first and navigation-last aggregate builds passed and produced the same Git tree.

Manual testing

A live Forge client/server acceptance pass is still required for permissions, refresh/reconnect, manual movement, every autopilot mode, hyperspace/takeoff/landing, and jump serialization.