feat(KB-231): add light mode support for dashboard UI

- Add CSS variables for light/dark theme support in global styles
- Remove hardcoded dark fallback colors from AgentLogViewer component
- Remove hardcoded dark fallback colors from SteeringTab comment bubbles and textarea
- Add changeset for patch release tracking
- Update ProviderIcon and NewTaskModal with proper theme-aware styling
- Clean up unused dashboard routes and tests

packages/dashboard/app/components/AgentLogViewer.tsx

@@ -51,7 +51,7 @@ export function AgentLogViewer({ entries, loading, executorModel, validatorModel
         overflowY: "auto",
         maxHeight: "500px",
         padding: "12px",
-        background: "var(--bg-secondary, #1a1a2e)",
+        background: "var(--bg-secondary)",
         borderRadius: "6px",
         whiteSpace: "pre-wrap",
         wordBreak: "break-word",
@@ -65,7 +65,7 @@ export function AgentLogViewer({ entries, loading, executorModel, validatorModel
           gap: "16px",
           padding: "8px 12px",
           marginBottom: "12px",
-          background: "var(--bg-tertiary, #252536)",
+          background: "var(--bg-tertiary)",
           borderRadius: "4px",
           fontSize: "12px",
           color: "var(--text-muted, #888)",

packages/dashboard/app/components/SteeringTab.tsx

@@ -99,7 +99,7 @@ export function SteeringTab({ task, addToast }: SteeringTabProps) {
                 style={{
                   marginTop: "4px",
                   padding: "8px 12px",
-                  background: "var(--bg-secondary, #1a1a2e)",
+                  background: "var(--bg-secondary)",
                   borderRadius: "6px",
                   border: "1px solid var(--border, #333)",
                   fontSize: "14px",
@@ -129,7 +129,7 @@ export function SteeringTab({ task, addToast }: SteeringTabProps) {
             padding: "12px",
             fontSize: "14px",
             fontFamily: "inherit",
-            background: "var(--bg-secondary, #1a1a2e)",
+            background: "var(--bg-secondary)",
             border: "1px solid var(--border, #333)",
             borderRadius: "6px",
             color: "inherit",