Transport non-player entities through gates too

GateTeleportListener previously only listened to PlayerMoveEvent, so
mobs, dropped items, minecarts, boats, and everything else that isn't
a player just walked/rolled/drifted straight through the event
horizon block with no effect. Added a Paper EntityMoveEvent handler
sharing the same one-way/outgoing-only matching, safe-landing, and
cooldown logic as the player path.

Non-player entities are restricted to same-server destinations - the
cross-server plugin-messaging protocol only carries a player's UUID
and look direction across the proxy hop, not arbitrary entity state,
so there's no way to hand off a mob or item to another backend.

README.md

@@ -60,12 +60,18 @@ material, unsealed interior, too far from the sign, etc.
 - **Left-click** the sign: dials the shown destination - chevrons light in sequence,
   then the interior becomes the event horizon (`gate.iris-open-material`, default
   water) and travel opens up. It auto-closes after `dialing.open-seconds`.
-- Travel is **one-way**: only the gate you dialed *from* can send you anywhere.
-  Walking into its event horizon teleports you to the destination, arriving just
-  clear of its iris (never inside it) and still facing whatever direction you were
-  already walking, so entering forward always means exiting forward. The
-  destination's horizon is visible but not walkable - stepping into it does nothing,
-  same as a real Stargate only running one direction at a time.
+- Travel is **one-way**: only the gate you dialed *from* can send anything anywhere.
+  Walking (or wandering, or drifting) into its event horizon teleports whatever
+  entered to the destination, arriving just clear of its iris (never inside it) and
+  still facing whatever direction it was already moving, so entering forward always
+  means exiting forward. The destination's horizon is visible but not walkable -
+  stepping into it does nothing, same as a real Stargate only running one direction
+  at a time.
+- Not just players - mobs, dropped items, minecarts, boats, arrows, anything that
+  moves through the event horizon gets sent through too. Non-player entities can
+  only travel to a same-server destination, though; there's no way to carry an
+  arbitrary entity's state across the Velocity/Bungee plugin-messaging hop, so a
+  cross-server gate just won't move anything but players.
 - The **iris shield** is a separate, physical thing from the wormhole connection.
   **Right-click a button placed directly below the sign** to toggle it. Closed means
   closed - `gate.iris-shield-material` (default bedrock), solid, blocking everything -