chore: scaffold pnpm workspace, container, deploy docs

Two-app pnpm workspace for the gashboard (mining dashboard) project:
@gashboard/api (Express 5 + TS) and @gashboard/web (Vue 3 + Vite + TS).
Shared tsconfig.base.json. Multi-stage Dockerfile (node:22.12-alpine,
non-root, healthchecked) and docker-compose.yml ready to deploy as a
Portainer Stack on Umbrel — joins umbrel_main_network so it can reach
the Datum container directly. .env.example documents every var; README
covers the Portainer deploy flow and the security posture.

Note: Dockerfile has a TODO marker to SHA256-pin the base image before
shipping to production.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

package.json

@@ -0,0 +1,16 @@
+{
+  "name": "gashboard",
+  "version": "0.1.0",
+  "private": true,
+  "description": "Datum mining dashboard for the four little boards that probably won't find a block",
+  "packageManager": "pnpm@9.12.3",
+  "scripts": {
+    "dev": "pnpm -r --parallel dev",
+    "build": "pnpm -r build",
+    "typecheck": "pnpm -r typecheck",
+    "lint": "pnpm -r lint"
+  },
+  "engines": {
+    "node": ">=22.12.0"
+  }
+}