feat: add community role grant and join prompt for players

- Grant Elysian Discord role to players on OAuth login (new and returning)
- Add inGuild flag to Player schema, seeded from role grant response
- Connect Discord Gateway WebSocket to keep inGuild in sync on join/leave
- Return inGuild from load endpoint; expose in game context
- Show join community modal once per session when inGuild is false

packages/types/src/interfaces/api.ts

@@ -70,6 +70,11 @@ interface LoginBonusResult {
 interface LoadResponse {
   state: GameState;
 
+  /**
+   * Whether the player is currently a member of the NHCarrigan Discord server.
+   */
+  inGuild: boolean;
+
   /**
    * Offline gold earned since last save (server-calculated).
    */