feat: initial scaffold - backend, frontend, Prisma schema, Docker

- Prisma schema: User, Session, RepoConfig, Preview, Job, WebhookToken, NoConfigComment, AdminSettings
- Backend: auth (login/logout/me/first-user setup), webhook handler with HMAC verification, EC2 service, SSH service, deploy pipeline, job queue worker, cron workers
- Frontend: Login with first-user detection, Dashboard, PreviewDetail with live log streaming, Settings, Repos config, Admin panel, SetupWizard, Privacy page
- Docker Compose and Dockerfile for self-hosted deployment
- Uses bcryptjs for Node 24 compatibility

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

backend/package.json

@@ -0,0 +1,40 @@
+{
+  "name": "pp-backend",
+  "version": "1.0.0",
+  "description": "PR Previews backend",
+  "private": true,
+  "scripts": {
+    "dev": "rimraf dist && esbuild \"src/**/*.ts\" --platform=node --sourcemap --ignore-annotations --format=cjs --target=es2022 --outdir=dist && cd dist && node index.js",
+    "build": "rimraf dist && esbuild \"src/**/*.ts\" --platform=node --sourcemap --ignore-annotations --format=cjs --target=es2022 --outdir=dist",
+    "start": "cd dist && node index.js",
+    "prod": "pnpm build && pnpm start",
+    "migrate": "prisma migrate dev --schema=../prisma/schema.prisma",
+    "migrate:deploy": "prisma migrate deploy --schema=../prisma/schema.prisma",
+    "generate": "prisma generate --schema=../prisma/schema.prisma"
+  },
+  "dependencies": {
+    "@aws-sdk/client-ec2": "^3.800.0",
+    "@aws-sdk/client-sts": "^3.800.0",
+    "@prisma/client": "^6.0.0",
+    "@rjweb/runtime-node": "^1.1.1",
+    "@rjweb/utils": "^1.12.29",
+    "@types/bcryptjs": "^3.0.0",
+    "@types/node": "^22.0.0",
+    "@types/ssh2": "^1.15.0",
+    "@types/ws": "^8.5.0",
+    "axios": "^1.7.0",
+    "bcryptjs": "^3.0.3",
+    "dotenv": "^17.0.0",
+    "esbuild": "^0.25.0",
+    "node-cron": "^3.0.3",
+    "pino": "^10.0.0",
+    "pino-pretty": "^13.0.0",
+    "prisma": "^6.0.0",
+    "rimraf": "^5.0.0",
+    "rjweb-server": "^9.8.6",
+    "ssh2": "^1.16.0",
+    "typescript": "^5.0.0",
+    "ws": "^8.18.0",
+    "zod": "^3.24.0"
+  }
+}