[feat](errorpages): add custom templates for HTTP errors and assets

- Implemented custom HTML templates for `400`, `404`, `500`, and `525` error pages with multilingual support.
- Added embedded file system for error page templates and assets.
- Introduced fallback mechanism to serve minimal plain text for missing error templates.
- Integrated TailwindCSS for styling error pages, with a build script in `package.json`.

tools/tailwind/input.css

@@ -0,0 +1,4 @@
+/* tools/tailwind/input.css */
+@tailwind base;
+@tailwind components;
+@tailwind utilities;

tools/tailwind/tailwind.config.cjs

@@ -0,0 +1,11 @@
+// tools/tailwind/tailwind.config.cjs
+/** @type {import('tailwindcss').Config} */
+module.exports = {
+    content: [
+        "./internal/errorpages/templates/*.html",
+    ],
+    theme: {
+        extend: {},
+    },
+    plugins: [],
+};