feat(P0-001): scaffold monorepo structure

pnpm workspaces, Turborepo, TypeScript strict, ESLint flat config,
Prettier, Vitest, husky + lint-staged. Placeholder packages for all
16 packages + 2 apps + 2 plugins.

Closes #1

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

apps/gateway/tsconfig.json

@@ -0,0 +1,13 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "compilerOptions": {
+    "outDir": "dist",
+    "rootDir": "src",
+    "experimentalDecorators": true,
+    "emitDecoratorMetadata": true,
+    "module": "CommonJS",
+    "moduleResolution": "Node"
+  },
+  "include": ["src/**/*"],
+  "exclude": ["node_modules", "dist"]
+}