Add project scaffolding and infrastructure config

pnpm monorepo with shared packages, server, and UI workspaces.
Includes Docker multi-stage build, Postgres compose, and root TypeScript/Vitest config.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,8 @@
+node_modules/
+dist/
+.env
+*.tsbuildinfo
+drizzle/meta/
+.vite/
+coverage/
+.DS_Store