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>

package.json

@@ -0,0 +1,24 @@
+{
+  "name": "paperclip",
+  "private": true,
+  "type": "module",
+  "scripts": {
+    "dev": "pnpm run --parallel dev:server dev:ui",
+    "dev:server": "pnpm --filter @paperclip/server dev",
+    "dev:ui": "pnpm --filter @paperclip/ui dev",
+    "build": "pnpm -r build",
+    "typecheck": "pnpm -r typecheck",
+    "test": "vitest",
+    "test:run": "vitest run",
+    "db:generate": "pnpm --filter @paperclip/db generate",
+    "db:migrate": "pnpm --filter @paperclip/db migrate"
+  },
+  "devDependencies": {
+    "typescript": "^5.7.3",
+    "vitest": "^3.0.5"
+  },
+  "engines": {
+    "node": ">=20"
+  },
+  "packageManager": "pnpm@9.15.4"
+}