feat: implement PageLoader component and register maritime loader as the default theme loader

libs/ui/src/lib/feedback/PageLoader.tsx

@@ -0,0 +1,26 @@
+import { Center, Loader, Stack, Text } from '@mantine/core';
+import { useTranslation } from 'react-i18next';
+
+interface PageLoaderProps {
+  /** Visible + accessible label. Defaults to the shared i18n "loading" string. */
+  label?: string;
+  /** Container height. Defaults to a full-page fill. */
+  height?: number | string;
+}
+
+/** The full-page/section loading state every screen should use instead of a bare `<Loader />`. */
+export function PageLoader({ label, height = '60vh' }: PageLoaderProps) {
+  const { t } = useTranslation();
+  const resolvedLabel = label ?? t('loading', 'Loading…');
+
+  return (
+    <Center h={height}>
+      <Stack align="center" gap="xs">
+        <Loader size={64} aria-label={resolvedLabel} />
+        <Text c="dimmed" size="sm">
+          {resolvedLabel}
+        </Text>
+      </Stack>
+    </Center>
+  );
+}