Replace TS game shell with Bevy/Rust client, add auth service, purge legacy archive

- Replace apps/game (TypeScript/Vite/R3F) with a Bevy 0.16 Rust client
  featuring main menu, star map, and flight states
- Add services/auth: Express + better-auth server with SpacetimeDB
  token exchange endpoint
- Delete archive/legacy-static/ (old JS demos, CSS, assets)
- Update docs pages (architecture, gameplay, roadmap, social, overview)
  to reflect Bevy pivot
- Clean up workspace config: remove apps/game from pnpm workspace,
  update dev scripts, tsconfig, and AGENTS.md files
- Add .vscode/settings.json for Rust tooling

services/auth/tsconfig.json

@@ -0,0 +1,7 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "compilerOptions": {
+    "types": ["node"]
+  },
+  "include": ["src"]
+}