feat: initialize sunrise with 100-player shared rooms

server/constants/multiplayer.ts

@@ -0,0 +1,7 @@
+/** Backend-only limits; shared room/wire settings live in src/constants/multiplayer.ts. */
+export const SERVER_LIMITS = {
+  movementBudgetSeconds: 0.5,
+  updateIntervalMs: 100,
+  weatherSampleMs: 60000,
+  defaultOrigins: ['http://localhost:3000', 'http://127.0.0.1:3000', 'http://localhost:5173', 'http://127.0.0.1:5173'],
+} as const;