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-plain-obj/index.js

@@ -0,0 +1,8 @@
+export default function isPlainObject(value) {
+	if (typeof value !== 'object' || value === null) {
+		return false;
+	}
+
+	const prototype = Object.getPrototypeOf(value);
+	return (prototype === null || prototype === Object.prototype || Object.getPrototypeOf(prototype) === null) && !(Symbol.toStringTag in value) && !(Symbol.iterator in value);
+}