feat: production deployment setup and hardcoded URL fixes

- Fix hardcoded localhost:8000 URLs in frontend to use relative /api/v1
  path (works with Nginx proxy in prod and VITE_API_URL in dev)
- Create production entrypoint (entrypoint.prod.sh) that runs migrations,
  seeds, and starts uvicorn with 4 workers (no --reload)
- Create comprehensive install.sh script for production deployment that
  generates secure .env, builds containers, waits for health, and
  optionally triggers initial MITRE sync
- Update docker-compose.prod.yml to use production entrypoint
- Update Dockerfile to make both entrypoints executable
- Remove init.ps1 (production will always be Linux)
- Update README with production deployment instructions

frontend/src/api/client.ts

@@ -1,7 +1,9 @@
 import axios, { type AxiosError } from "axios";
 
+const API_BASE_URL = import.meta.env.VITE_API_URL || "/api/v1";
+
 const client = axios.create({
-  baseURL: "http://localhost:8000/api/v1",
+  baseURL: API_BASE_URL,
   headers: { "Content-Type": "application/json" },
 });