fix: Fix product page syntax errors

1. Remove duplicate/broken code in product tables section
2. Fix PostCSS config for Tailwind 4
3. Add @tailwindcss/postcss dependency
4. Remove --production flag from Dockerfile (sharp required)

All fixes enable successful Docker build with favicon working.

node_modules/is-docker/cli.js

@@ -0,0 +1,5 @@
+#!/usr/bin/env node
+import process from 'node:process';
+import isDocker from './index.js';
+
+process.exitCode = isDocker() ? 0 : 2;