Restructure into pnpm monorepo with game shell, docs, and SpacetimeDB backend

- Restructure flat static prototype into pnpm workspace monorepo
- apps/game: playable shell with R3F 3D scene, HUD, SpacetimeDB connection
- apps/docs: design docs and prototypes
- apps/site: landing page
- packages/ui: shared Button and Panel primitives
- services/spacetimedb: backend module (9 tables, 11 reducers)
- Archive legacy static files to archive/legacy-static/
- Game loop: connect, undock, target, approach, dock, mine, sell
- Add pnpm-workspace.yaml, tsconfig.base.json, spacetime.json

services/spacetimedb/package.json

@@ -0,0 +1,12 @@
+{
+  "name": "@void-nav/spacetimedb",
+  "private": true,
+  "version": "0.1.0",
+  "type": "module",
+  "dependencies": {
+    "spacetimedb": "^2.3.0"
+  },
+  "devDependencies": {
+    "typescript": "^5.8.3"
+  }
+}