feat(highlights): add citation attribution to highlight items

- Create HighlightCitation component to show source attribution
- For nostr-native content: display as '— Author, Article Title'
- For web URLs: display hostname as '— domain.com'
- Automatically resolves article titles from event references
- Resolves author names from profile data
- Add styling for citation line below highlight text
- Keep code DRY by reusing existing articleTitleResolver service

src/components/HighlightCitation.tsx

@@ -0,0 +1,87 @@
+import React, { useState, useEffect } from 'react'
+import { RelayPool } from 'applesauce-relay'
+import { useEventModel } from 'applesauce-react/hooks'
+import { Models } from 'applesauce-core'
+import { nip19 } from 'nostr-tools'
+import { fetchArticleTitle } from '../services/articleTitleResolver'
+
+interface HighlightCitationProps {
+  eventReference?: string
+  urlReference?: string
+  authorPubkey?: string
+  relayPool?: RelayPool | null
+}
+
+export const HighlightCitation: React.FC<HighlightCitationProps> = ({
+  eventReference,
+  urlReference,
+  authorPubkey,
+  relayPool
+}) => {
+  const [articleTitle, setArticleTitle] = useState<string>()
+  const authorProfile = useEventModel(Models.ProfileModel, authorPubkey ? [authorPubkey] : null)
+  
+  useEffect(() => {
+    if (!eventReference || !relayPool) {
+      return
+    }
+    
+    const loadTitle = async () => {
+      try {
+        // Convert eventReference to naddr if needed
+        let naddr: string
+        if (eventReference.includes(':')) {
+          const parts = eventReference.split(':')
+          const kind = parseInt(parts[0])
+          const pubkey = parts[1]
+          const identifier = parts[2] || ''
+          
+          naddr = nip19.naddrEncode({
+            kind,
+            pubkey,
+            identifier
+          })
+        } else {
+          naddr = eventReference
+        }
+        
+        const title = await fetchArticleTitle(relayPool, naddr)
+        if (title) {
+          setArticleTitle(title)
+        }
+      } catch (error) {
+        console.error('Failed to load article title:', error)
+      }
+    }
+    
+    loadTitle()
+  }, [eventReference, relayPool])
+  
+  const authorName = authorProfile?.name || authorProfile?.display_name
+  
+  // For nostr-native content with article reference
+  if (eventReference && (authorName || articleTitle)) {
+    return (
+      <div className="highlight-citation">
+        — {authorName || 'Unknown'}{articleTitle ? `, ${articleTitle}` : ''}
+      </div>
+    )
+  }
+  
+  // For web URLs
+  if (urlReference) {
+    try {
+      const url = new URL(urlReference)
+      return (
+        <div className="highlight-citation">
+          — {url.hostname}
+        </div>
+      )
+    } catch {
+      return null
+    }
+  }
+  
+  return null
+}
+

src/components/HighlightItem.tsx

@@ -15,6 +15,7 @@ import { createDeletionRequest } from '../services/deletionService'
 import ConfirmDialog from './ConfirmDialog'
 import { getNostrUrl } from '../config/nostrGateways'
 import CompactButton from './CompactButton'
+import { HighlightCitation } from './HighlightCitation'
 
 interface HighlightWithLevel extends Highlight {
   level?: 'mine' | 'friends' | 'nostrverse'
@@ -338,6 +339,13 @@ export const HighlightItem: React.FC<HighlightItemProps> = ({
           {highlight.content}
         </blockquote>
         
+        <HighlightCitation
+          eventReference={highlight.eventReference}
+          urlReference={highlight.urlReference}
+          authorPubkey={highlight.author}
+          relayPool={relayPool}
+        />
+        
         {highlight.comment && (
           <div className="highlight-comment">
             {highlight.comment}

src/styles/layout/highlights.css

@@ -128,6 +128,7 @@
 
 .highlight-content { flex: 1; display: flex; flex-direction: column; gap: 0.5rem; padding: 2.25rem 0.75rem 2.5rem; }
 .highlight-text { margin: 0; padding: 0 0 0 1.25rem; font-style: italic; color: var(--color-text); line-height: 1.6; border-left: none; font-size: 0.95rem; }
+.highlight-citation { margin-left: 1.25rem; font-size: 0.8rem; color: var(--color-text-secondary); font-style: normal; padding-top: 0.25rem; }
 .highlight-comment { margin-top: 0.5rem; margin-left: 1.25rem; padding: 0.75rem; border-left: 3px solid; border-radius: 4px; font-size: 0.875rem; color: var(--color-text); line-height: 1.5; }
 
 /* Level-colored comments */