Refactor frontend components to use new icon imports and improve default values

- Updated `EnhancedMetricCard` to set a default accent color to blue.
- Replaced `lucide-react` icons with custom icons in `LinkResults`, `OptimizationScores`, and various pages in the Automation and Optimizer sections.
- Enhanced button layouts in `AutomationRules`, `Tasks`, and `ContentSelector` for better alignment and user experience.
- Improved loading indicators across components for a more consistent UI experience.

frontend/src/components/dashboard/EnhancedMetricCard.tsx

@@ -62,7 +62,7 @@ export default function EnhancedMetricCard({
   subtitle,
   trend,
   icon,
-  accentColor,
+  accentColor = "blue", // Default to blue if not provided
   href,
   onClick,
   tooltip,
@@ -70,7 +70,7 @@ export default function EnhancedMetricCard({
   className = "",
 }: MetricCardProps) {
   const [isHovered, setIsHovered] = useState(false);
-  const colors = accentColors[accentColor];
+  const colors = accentColors[accentColor] || accentColors.blue; // Fallback to blue if invalid
 
   const formatValue = (val: string | number): string => {
     if (typeof val === "number") {