feat: RichText component for safe PocketBase HTML rendering

Add html-react-parser-backed RichText component that converts HTML
strings from PocketBase rich-text fields into React elements without
dangerouslySetInnerHTML. Replace raw <p> render in IntroSection and
BioSection, and drop the invalid slug filters those collections lacked.

src/widgets/IntroSection/ui/IntroSection/IntroSection.tsx

@@ -1,23 +1,18 @@
 import { notFound } from 'next/navigation';
 import type { PageContentRecord } from '$shared/api';
 import { getFirstRecord } from '$shared/api';
+import { RichText } from '$shared/ui';
 
 /**
  * Intro section component.
  * Displays primary introduction content from PocketBase.
  */
 export default async function IntroSection() {
-  const data = await getFirstRecord<PageContentRecord>('intro', {
-    filter: 'slug = "intro"',
-  });
+  const data = await getFirstRecord<PageContentRecord>('intro');
 
   if (!data) {
     notFound();
   }
 
-  return (
-    <div className="prose prose-lg dark:prose-invert max-w-none">
-      <p>{data.content}</p>
-    </div>
-  );
+  return <RichText html={data.content} className="prose prose-lg max-w-none" />;
 }