feat: add flight mode indicator to offline-created highlights

- Add isOfflineCreated property to Highlight type
- Set flag when highlight is created in local-only mode
- Display small plane icon in highlight sidebar for offline-created highlights
- Lighter amber color (#fbbf24) to distinguish from Local badge
- Tooltip: 'Created while in flight mode'
- Visual indicator helps users track which highlights need syncing

src/components/HighlightItem.tsx

@@ -1,6 +1,6 @@
 import React, { useEffect, useRef } from 'react'
 import { FontAwesomeIcon } from '@fortawesome/react-fontawesome'
-import { faQuoteLeft, faExternalLinkAlt, faHouseSignal } from '@fortawesome/free-solid-svg-icons'
+import { faQuoteLeft, faExternalLinkAlt, faHouseSignal, faPlane } from '@fortawesome/free-solid-svg-icons'
 import { Highlight } from '../types/highlights'
 import { formatDistanceToNow } from 'date-fns'
 import { useEventModel } from 'applesauce-react/hooks'
@@ -101,6 +101,15 @@ export const HighlightItem: React.FC<HighlightItemProps> = ({ highlight, onSelec
             </>
           )}
           
+          {highlight.isOfflineCreated && (
+            <>
+              <span className="highlight-meta-separator">•</span>
+              <span className="highlight-offline-indicator" title="Created while in flight mode">
+                <FontAwesomeIcon icon={faPlane} />
+              </span>
+            </>
+          )}
+          
           {sourceLink && (
             <a
               href={sourceLink}

src/index.css

@@ -1623,6 +1623,14 @@ body {
   border: 1px solid rgba(245, 158, 11, 0.3);
 }
 
+.highlight-offline-indicator {
+  display: inline-flex;
+  align-items: center;
+  color: #fbbf24;
+  font-size: 0.8rem;
+  opacity: 0.8;
+}
+
 .highlight-local-text {
   font-size: 0.75rem;
   text-transform: uppercase;

src/services/highlightCreationService.ts

@@ -152,6 +152,7 @@ export async function createHighlight(
   const highlight = eventToHighlight(signedEvent)
   highlight.publishedRelays = actualPublishedRelays
   highlight.isLocalOnly = isLocalOnly
+  highlight.isOfflineCreated = isLocalOnly // Mark as created offline if local-only
   
   // Return the highlight for immediate UI updates
   return highlight

src/types/highlights.ts

@@ -18,5 +18,6 @@ export interface Highlight {
   // Relay tracking for offline/local-only highlights
   publishedRelays?: string[] // URLs of relays that acknowledged this event
   isLocalOnly?: boolean // true if only published to local relays
+  isOfflineCreated?: boolean // true if created while in flight mode (offline)
 }