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

apps/game/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "void-nav"
+version = "0.1.0"
+edition = "2021"
+description = "VOID::NAV — Space exploration RPG built with Bevy"
+
+[dependencies]
+bevy = "0.16"
+rand = "0.8"
+
+# Optimize dependencies in dev for better FPS
+[profile.dev.package."*"]
+opt-level = 3