Fix missing and broken "Follow" button on reposts (#7056)

## Issue
6776 Missing follow button on channel reposts

- Missing:
    - Fix: For reposts, `parseURI` will fail to determine if it's a channel because the URL doesn't have enough info. Determine from the claim object instead.
- Not working in Channel Page:
    - Fix: The repost uri doesn't link back to the source channel, so we'll need to handle it.

ui/component/claimPreview/view.jsx

@@ -195,8 +195,12 @@ const ClaimPreview = forwardRef<any, {}>((props: Props, ref: any) => {
     claim.value.stream_type &&
     // $FlowFixMe
     (claim.value.stream_type === 'audio' || claim.value.stream_type === 'video');
-  const isChannelUri = isValid ? parseURI(uri).isChannel : false;
+  const isChannelUri = claim ? claim.value_type === 'channel' : false;
   const signingChannel = claim && claim.signing_channel;
+  const repostedChannelUri =
+    claim && claim.repost_channel_url && claim.value_type === 'channel'
+      ? claim.permanent_url || claim.canonical_url
+      : undefined;
 
   // Get channel title ( use name as fallback )
   let channelTitle = null;
@@ -478,7 +482,9 @@ const ClaimPreview = forwardRef<any, {}>((props: Props, ref: any) => {
                         )}
 
                         {isChannelUri && !channelIsBlocked && !claimIsMine && (
-                          <SubscribeButton uri={uri.startsWith('lbry://') ? uri : `lbry://${uri}`} />
+                          <SubscribeButton
+                            uri={repostedChannelUri || (uri.startsWith('lbry://') ? uri : `lbry://${uri}`)}
+                          />
                         )}
 
                         {includeSupportAction && <ClaimSupportButton uri={uri} />}

ui/component/claimPreviewTile/view.jsx

@@ -97,6 +97,7 @@ function ClaimPreviewTile(props: Props) {
   const shouldFetch = claim === undefined;
   const thumbnailUrl = useGetThumbnail(uri, claim, streamingUrl, getFile, placeholder) || thumbnail;
   const canonicalUrl = claim && claim.canonical_url;
+  const permanentUrl = claim && claim.permanent_url;
   let navigateUrl = formatLbryUrlForWeb(canonicalUrl || uri || '/');
   const listId = collectionId || collectionClaimId;
   if (listId) {
@@ -123,6 +124,7 @@ function ClaimPreviewTile(props: Props) {
   const isChannel = claim && claim.value_type === 'channel';
   const channelUri = !isChannel ? signingChannel && signingChannel.permanent_url : claim && claim.permanent_url;
   const channelTitle = signingChannel && ((signingChannel.value && signingChannel.value.title) || signingChannel.name);
+  const repostedChannelUri = isRepost && isChannel ? permanentUrl || canonicalUrl : undefined;
 
   // Aria-label value for claim preview
   let ariaLabelData = isChannel ? title : formatClaimPreviewTitle(title, channelTitle, date, mediaDuration);
@@ -250,7 +252,7 @@ function ClaimPreviewTile(props: Props) {
         <div className="claim-tile__info">
           {isChannel ? (
             <div className="claim-tile__about--channel">
-              <SubscribeButton uri={uri} />
+              <SubscribeButton uri={repostedChannelUri || uri} />
             </div>
           ) : (
             <React.Fragment>