Add problems plugin v3.0.0

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

user/plugins/problems/scss/spectre-icons.scss

@@ -0,0 +1,10 @@
+// Variables and mixins
+@import "variables";
+@import "mixins";
+
+/*! Spectre.css Icons v#{$version} | MIT License | github.com/picturepan2/spectre */
+// Icons
+@import "icons/icons-core";
+@import "icons/icons-navigation";
+@import "icons/icons-action";
+@import "icons/icons-object";