chore: update css lint rules, remove unused files

web/package.json

@@ -23,6 +23,7 @@
 		"refs-dom-audit": "node scripts/audit-dom.mjs"
 	},
 	"devDependencies": {
+		"@csstools/postcss-global-data": "^4.0.0",
 		"@eslint/js": "^10.0.1",
 		"@panmdaa/colors": "^0.4.2",
 		"@sveltejs/adapter-static": "^3.0.10",
@@ -35,6 +36,7 @@
 		"globals": "^17.11.0",
 		"playwright": "^1.62.1",
 		"postcss": "^8.5.26",
+		"postcss-custom-media": "^12.0.1",
 		"prettier": "^3.9.6",
 		"prettier-plugin-svelte": "^4.1.1",
 		"stylelint": "^17.14.1",