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/package.json

@@ -0,0 +1,31 @@
+{
+  "name": "frontend",
+  "private": true,
+  "version": "0.0.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "vue-tsc -b && vite build",
+    "preview": "vite preview",
+    "test": "vitest"
+  },
+  "dependencies": {
+    "@tailwindcss/vite": "^4.3.1",
+    "pinia": "^3.0.4",
+    "tailwindcss": "^4.3.1",
+    "vue": "^3.5.34",
+    "vue-router": "^5.1.0"
+  },
+  "devDependencies": {
+    "@types/node": "^24.12.3",
+    "@vitejs/plugin-vue": "^6.0.6",
+    "@vue/test-utils": "^2.4.11",
+    "@vue/tsconfig": "^0.9.1",
+    "jsdom": "^29.1.1",
+    "prettier": "^3.8.4",
+    "typescript": "~6.0.2",
+    "vite": "^8.0.12",
+    "vitest": "^4.1.9",
+    "vue-tsc": "^3.2.8"
+  }
+}