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/components/tools/removePages/RemovePagesSettings.tsx

@@ -0,0 +1,40 @@
+import { Stack, TextInput } from "@mantine/core";
+import { useTranslation } from "react-i18next";
+import { RemovePagesParameters } from "@app/hooks/tools/removePages/useRemovePagesParameters";
+import { validatePageNumbers } from "@app/utils/pageSelection";
+
+interface RemovePagesSettingsProps {
+  parameters: RemovePagesParameters;
+  onParameterChange: <K extends keyof RemovePagesParameters>(key: K, value: RemovePagesParameters[K]) => void;
+  disabled?: boolean;
+}
+
+const RemovePagesSettings = ({ parameters, onParameterChange, disabled = false }: RemovePagesSettingsProps) => {
+  const { t } = useTranslation();
+
+  const handlePageNumbersChange = (value: string) => {
+    // Allow user to type naturally - don't normalize input in real-time
+    onParameterChange('pageNumbers', value);
+  };
+  console.log('Current pageNumbers input:', parameters.pageNumbers, disabled);
+
+  // Check if current input is valid
+  const isValid = validatePageNumbers(parameters.pageNumbers || '');
+  const hasValue = (parameters?.pageNumbers?.trim().length ?? 0) > 0;
+
+  return (
+    <Stack gap="md">
+      <TextInput
+        label={t('removePages.pageNumbers.label', 'Pages to Remove')}
+        value={parameters.pageNumbers || ''}
+        onChange={(event) => handlePageNumbersChange(event.currentTarget.value)}
+        placeholder={t('removePages.pageNumbers.placeholder', 'e.g., 1,3,5-8,10')}
+        disabled={disabled}
+        required
+        error={hasValue && !isValid ? t('removePages.pageNumbers.error', 'Invalid page number format. Use numbers, ranges (1-5), or mathematical expressions (2n+1)') : undefined}
+      />
+    </Stack>
+  );
+};
+
+export default RemovePagesSettings;