fix(ui): rebind economics panel toggle from E to N (#124 review R2)

E is claimed by InputMap "interact" action — InputMapper consumes
it before _unhandled_key_input. N is free, adjacent to M (star map),
reads as "Numbers" for the economics monitor.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/scripts/main.gd

@@ -172,8 +172,8 @@ func _unhandled_key_input(event: InputEvent) -> void:
 		if event is InputEventKey and event.keycode == KEY_M:
 			if star_map:
 				star_map.toggle_visible()
-		elif event is InputEventKey and event.keycode == KEY_E:
-			# #824: E — toggle Economics Monitor implant panel
+		elif event is InputEventKey and event.keycode == KEY_N:
+			# #824: N — toggle Economics Monitor implant panel (E is bound to interact)
 			if economics_panel:
 				economics_panel.toggle_visible()
 		elif event is InputEventKey and event.keycode == KEY_BRACKETLEFT:

client/ui/implant/economics_panel.gd

@@ -257,7 +257,7 @@ func _rebuild_panel() -> void:
 	_panel.add_component(_placeholder_notice)
 
 	_panel.add_component(ImplantSeparator.new())
-	_panel.add_component(ImplantTextBlock.new("[ ] select system · E close"))
+	_panel.add_component(ImplantTextBlock.new("[ ] select system · N close"))
 
 
 func _current_node() -> Dictionary: