Restructure frontend code to allow for extensions (#4721)

# Description of Changes
Move frontend code into `core` folder and add infrastructure for
`proprietary` folder to include premium, non-OSS features

frontend/src/core/hooks/useToolNavigation.ts

@@ -0,0 +1,46 @@
+import { useCallback } from 'react';
+import { ToolRegistryEntry, getToolUrlPath } from '@app/data/toolsTaxonomy';
+import { useToolWorkflow } from '@app/contexts/ToolWorkflowContext';
+import { handleUnlessSpecialClick } from '@app/utils/clickHandlers';
+import { ToolId } from '@app/types/toolId';
+
+export interface ToolNavigationProps {
+  /** Full URL for the tool (for href attribute) */
+  href: string;
+  /** Click handler that maintains SPA behavior */
+  onClick: (e: React.MouseEvent) => void;
+}
+
+/**
+ * Hook that provides URL and navigation handlers for tools
+ * Enables right-click "Open in New Tab" while maintaining SPA behavior for regular clicks
+ */
+export function useToolNavigation(): {
+  getToolNavigation: (toolId: string, tool: ToolRegistryEntry) => ToolNavigationProps;
+} {
+  const { handleToolSelect } = useToolWorkflow();
+
+  const getToolNavigation = useCallback((toolId: string, tool: ToolRegistryEntry): ToolNavigationProps => {
+    // Generate SSR-safe relative path
+    const path = getToolUrlPath(toolId);
+    const href = path; // Relative path, no window.location needed
+
+    // Click handler that maintains SPA behavior
+    const onClick = (e: React.MouseEvent) => {
+      handleUnlessSpecialClick(e, () => {
+        // Handle external links normally
+        if (tool.link) {
+          window.open(tool.link, '_blank', 'noopener,noreferrer');
+          return;
+        }
+
+        // Use SPA navigation for internal tools
+        handleToolSelect(toolId as ToolId);
+      });
+    };
+
+    return { href, onClick };
+  }, [handleToolSelect]);
+
+  return { getToolNavigation };
+}