Add cashtag support for stock ticker discussions (#9689)

* Add cashtag support for stock ticker discussions

Display cashtags ($TICKER format) as clickable links with dedicated menu actions and search feed, alongside hashtags. Includes composer highlighting and proper formatting.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

* Fix cashtag search query to use # prefix

Cashtags need to be searched as "#$BTC" rather than just "$BTC" to work
with the search API.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* Update @atproto/api to 0.18.14 with cashtag support

The updated package includes native CASHTAG_REGEX detection for stock
ticker symbols like $AAPL and $BTC.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* Fix todo, remove redundant validation

---------

Co-authored-by: Claude Haiku 4.5 <noreply@anthropic.com>
Co-authored-by: Eric Bailey <git@esb.lol>

src/screens/Hashtag.tsx

@@ -46,13 +46,22 @@ export default function HashtagScreen({
   const {tag, author} = route.params
   const {_} = useLingui()
 
-  const fullTag = React.useMemo(() => {
-    return `#${decodeURIComponent(tag)}`
+  const decodedTag = React.useMemo(() => {
+    return decodeURIComponent(tag)
   }, [tag])
 
+  const isCashtag = decodedTag.startsWith('$')
+
+  const fullTag = React.useMemo(() => {
+    // Cashtags already include the $ prefix, hashtags need # added
+    return isCashtag ? decodedTag : `#${decodedTag}`
+  }, [decodedTag, isCashtag])
+
   const headerTitle = React.useMemo(() => {
-    return enforceLen(fullTag.toLowerCase(), 24, true, 'middle')
-  }, [fullTag])
+    // Keep cashtags uppercase, lowercase hashtags
+    const displayTag = isCashtag ? fullTag.toUpperCase() : fullTag.toLowerCase()
+    return enforceLen(displayTag, 24, true, 'middle')
+  }, [fullTag, isCashtag])
 
   const sanitizedAuthor = React.useMemo(() => {
     if (!author) return
@@ -172,10 +181,14 @@ function HashtagScreenTab({
   const {hasSession} = useSession()
   const trackPostView = usePostViewTracking('Hashtag')
 
+  const isCashtag = fullTag.startsWith('$')
+
   const queryParam = React.useMemo(() => {
-    if (!author) return fullTag
-    return `${fullTag} from:${author}`
-  }, [fullTag, author])
+    // Cashtags need # prefix for search: "#$BTC" or "#$BTC from:author"
+    const searchTag = isCashtag ? `#${fullTag}` : fullTag
+    if (!author) return searchTag
+    return `${searchTag} from:${author}`
+  }, [fullTag, author, isCashtag])
 
   const {
     data,
@@ -255,7 +268,7 @@ function HashtagScreenTab({
           isError={isError}
           onRetry={refetch}
           emptyType="results"
-          emptyMessage={_(msg`We couldn't find any results for that hashtag.`)}
+          emptyMessage={_(msg`We couldn't find any results for that tag.`)}
         />
       ) : (
         <List