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/package.json

@@ -0,0 +1,24 @@
+{
+  "name": "@void-nav/auth",
+  "private": true,
+  "version": "0.1.0",
+  "type": "module",
+  "scripts": {
+    "dev": "tsx watch src/index.ts",
+    "start": "tsx src/index.ts",
+    "migrate": "npx auth migrate"
+  },
+  "dependencies": {
+    "better-auth": "^1.2.0",
+    "better-sqlite3": "^12.0.0",
+    "cors": "^2.8.5",
+    "express": "^5.1.0"
+  },
+  "devDependencies": {
+    "@types/better-sqlite3": "^7.6.13",
+    "@types/cors": "^2.8.19",
+    "@types/express": "^5.0.3",
+    "tsx": "^4.19.4",
+    "typescript": "^5.8.3"
+  }
+}