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/diff/CONTRIBUTING.md

@@ -0,0 +1,28 @@
+## Building and testing
+
+```
+yarn
+yarn test
+```
+
+To run tests in a *browser* (for instance to test compatibility with Firefox, with Safari, or with old browser versions), run `yarn karma start`, then open http://localhost:9876/ in the browser you want to test in. Results of the test run will appear in the terminal where `yarn karma start` is running.
+
+If you notice any problems, please report them to the GitHub issue tracker at
+[http://github.com/kpdecker/jsdiff/issues](http://github.com/kpdecker/jsdiff/issues).
+
+## Releasing
+
+Run a test in Firefox via the procedure above before releasing.
+
+A full release may be completed by first updating the `"version"` property in package.json, then running the following:
+
+```
+yarn clean
+yarn build
+yarn publish
+```
+
+After releasing, remember to:
+* commit the `package.json` change and push it to GitHub
+* create a new version tag on GitHub
+* update `diff.js` on the `gh-pages` branch to the latest built version from the `dist/` folder.