build(deps-dev): update postcss to 8.5.29

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

package.json

@@ -100,7 +100,7 @@
     "karma-coverage": "~2.2.0",
     "karma-jasmine": "~5.1.0",
     "karma-jasmine-html-reporter": "^2.3.0",
-    "postcss": "^8.5.14",
+    "postcss": "^8.5.29",
     "postcss-selector-parser": "^7.1.1",
     "prettier": "^3.8.1",
     "sharp": "^0.35.5",