fix: Docker build and runtime fixes

- Fix duplicate 'signature' variable in webhooks.ts
- Add Prisma binary target for Alpine Linux
- Fix tsconfig path alias (@/* -> ./src/*)
- Add missing next-themes dependency
- Add build args for NEXT_PUBLIC_* env vars
- Fix SSR issues with zustand and providers
- Add providers-wrapper with dynamic ssr:false import
- Add SSL certs and public dir for nginx
- Update Dockerfiles for proper Prisma engine handling

frontend/next.config.js

@@ -1,7 +1,11 @@
 /** @type {import('next').NextConfig} */
+const path = require('path');
+
 const nextConfig = {
-  experimental: {
-    appDir: true,
+  webpack: (config) => {
+    config.resolve.alias['@'] = path.join(__dirname, 'src');
+    config.parallelism = 1;
+    return config;
   },
   async rewrites() {
     return [