Add R2 image storage, upload endpoint, and CDN support

- Backend: R2StorageService, upload controller (POST /api/upload)
- Frontend: CDN url helper, NEXT_PUBLIC_CDN_URL build arg
- Deploy: pass R2 secrets from Woodpecker CI to containers via .env
- Docs: update CLAUDE.md with CDN and upload conventions

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

frontend/next.config.ts

@@ -2,6 +2,11 @@ import type { NextConfig } from "next";
 
 const nextConfig: NextConfig = {
   output: "standalone",
+  images: {
+    remotePatterns: [
+      { protocol: "https", hostname: "cdn.goodbrick.com.ua" },
+    ],
+  },
   async rewrites() {
     const apiUrl = process.env.LOCAL_API_URL;
     if (!apiUrl) return [];