chore: initial monorepo scaffold

Setup pnpm workspaces with apps/{web,api} placeholders and shared
packages: tsconfig, eslint-config, shared, ui, db. Includes Prettier,
ESLint, Husky pre-commit, lint-staged, EditorConfig, VSCode settings.

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

packages/tsconfig/nextjs.json

@@ -0,0 +1,12 @@
+{
+  "$schema": "https://json.schemastore.org/tsconfig",
+  "display": "Next.js",
+  "extends": "./base.json",
+  "compilerOptions": {
+    "lib": ["DOM", "DOM.Iterable", "ES2022"],
+    "jsx": "preserve",
+    "allowJs": true,
+    "noEmit": true,
+    "plugins": [{ "name": "next" }]
+  }
+}