feat: add ResourceNode system with target selection and reservation

Phase 1-2 of the ResourceNode migration plan:

- Create ResourceNode class (world/resource_nodes/) with extraction,
  reservation, nearest-available selection, and debug label
- Place 4 resource instances in main.tscn (2 berry bushes, 2 trees)
- Add target_id to SimNPC for tracking which node an NPC is using
- Add set_npc_target_id and release_npc_reservation to SimulationManager
  with cleanup on task change, completion, and death
- Update WorldViewManager to query available ResourceNodes first,
  falling back to zone markers with a logged warning

.gitignore

@@ -48,6 +48,7 @@ crash_handler*
 *.temp
 *.tmp
 *~
+~*.dll
 .#*
 \#*\#