feat: bootstrap OSDB full-stack skeleton (story #01)

- Go backend: Echo v4 + pgxpool + embedded golang-migrate; health endpoints
  at /health and /api/v1/health; TDD health handler (httptest)
- Vue 3 frontend: Vite + TypeScript + Pinia + vue-router + Tailwind CSS v4;
  TDD HelloWorld component (@vue/test-utils + jsdom + vitest)
- Infra: docker-compose postgres:16 with env-interpolated credentials;
  Makefile with dev-db health-wait loop, migrate-up/down, run, test, fmt
- embed.FS migrations at backend/migrations/ (000001 no-op baseline)

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

frontend/tsconfig.app.json

@@ -0,0 +1,14 @@
+{
+  "extends": "@vue/tsconfig/tsconfig.dom.json",
+  "compilerOptions": {
+    "tsBuildInfoFile": "./node_modules/.tmp/tsconfig.app.tsbuildinfo",
+    "types": ["vite/client"],
+
+    /* Linting */
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "erasableSyntaxOnly": true,
+    "noFallthroughCasesInSwitch": true
+  },
+  "include": ["src/**/*.ts", "src/**/*.tsx", "src/**/*.vue"]
+}