feat: add backend infrastructure - Express server, auth, CRUD APIs, DB migrations

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

package.json

@@ -0,0 +1,24 @@
+{
+  "name": "shokuninmarche",
+  "version": "1.0.0",
+  "description": "職人マルシェ - Japanese Craft Marketplace",
+  "main": "server.js",
+  "scripts": {
+    "start": "node server.js",
+    "dev": "nodemon server.js",
+    "migrate": "node src/db/migrate.js"
+  },
+  "dependencies": {
+    "bcryptjs": "^2.4.3",
+    "compression": "^1.7.4",
+    "cors": "^2.8.5",
+    "express": "^4.18.2",
+    "express-rate-limit": "^7.1.5",
+    "express-validator": "^7.0.1",
+    "helmet": "^7.1.0",
+    "ioredis": "^5.3.2",
+    "jsonwebtoken": "^9.0.2",
+    "pg": "^8.11.3",
+    "uuid": "^9.0.0"
+  }
+}