chore(deps): migrate to Bevy 0.18

- BorderRadius is no longer a Component; moved into Node.border_radius
  field at all 15 spawn sites across 6 plugin files
- Events<T> renamed to Messages<T> in test code (12 files)
- KeyboardEvents SystemParam renamed to KeyboardMessages to match the
  MessageWriter rename done in the 0.17 hop
- WindowResolution::from((f32,f32)) removed; use (u32,u32) tuple in main.rs

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

.sqlx/query-36bab3ca8f126c66a6f4865d2699702689518bd3a796c374f932aba0434a4c94.json

@@ -0,0 +1,12 @@
+{
+  "db_name": "SQLite",
+  "query": "UPDATE users SET leaderboard_opt_in = 0 WHERE id = ?",
+  "describe": {
+    "columns": [],
+    "parameters": {
+      "Right": 1
+    },
+    "nullable": []
+  },
+  "hash": "36bab3ca8f126c66a6f4865d2699702689518bd3a796c374f932aba0434a4c94"
+}