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/shared/ui/RichText/index.ts

@@ -0,0 +1 @@
+export { RichText } from './ui/RichText';