Fix missing embeds in fallback posts and thread fallback

- Add resolveRecordEmbeds() to convert raw blob refs into CDN URLs for
  external link cards, images, videos, and recordWithMedia embeds
- Wire resolved embeds into buildSyntheticPostView and
  buildSyntheticEmbedViewRecord so fallback posts render media
- Fix thread fallback: intercept threadItemNotFound from AppView and
  load post via Slingshot instead of showing "Post not found"
- Add moderation checks to thread fallback to prevent bypassing
  takedowns/suspensions
- Add quoteCount from Constellation backlink data
- Use record createdAt as indexedAt to prevent false archived post warning
- Change "Bluesky" to "Blacksky" in archived post dialog

Author: rudyfraser

src/components/Post/Embed/index.tsx

@@ -13,6 +13,7 @@ import {useQueryClient} from '@tanstack/react-query'
 
 import {makeProfileLink} from '#/lib/routes/links'
 import {useModerationOpts} from '#/state/preferences/moderation-opts'
+import {useEmbedFallback} from '#/state/queries/embed-fallback'
 import {unstableCacheProfileView} from '#/state/queries/profile'
 import {useSession} from '#/state/session'
 import {Link} from '#/view/com/util/Link'
@@ -174,11 +175,7 @@ function RecordEmbed({
       )
     }
     case 'post_not_found': {
-      return (
-        <PostPlaceholderText>
-          <Trans>Deleted</Trans>
-        </PostPlaceholderText>
-      )
+      return <PostNotFoundEmbed embed={embed} {...rest} />
     }
     case 'post_blocked': {
       return (
@@ -217,6 +214,49 @@ export function PostDetachedEmbed({
   )
 }
 
+/*
+ * Attempts Slingshot fallback before showing "Deleted" for embedded posts
+ * that our appview hasn't synced yet.
+ */
+function PostNotFoundEmbed({
+  embed,
+  ...rest
+}: CommonProps & {embed: EmbedType<'post_not_found'>}) {
+  const {data: fallbackRecord, isLoading} = useEmbedFallback({
+    uri: embed.view.uri,
+  })
+
+  if (isLoading) {
+    return (
+      <PostPlaceholderText>
+        <Trans>Loading...</Trans>
+      </PostPlaceholderText>
+    )
+  }
+
+  if (fallbackRecord) {
+    return (
+      <QuoteEmbed
+        {...rest}
+        embed={{type: 'post', view: fallbackRecord}}
+        viewContext={
+          rest.viewContext === PostEmbedViewContext.Feed
+            ? QuoteEmbedViewContext.FeedEmbedRecordWithMedia
+            : undefined
+        }
+        isWithinQuote={rest.isWithinQuote}
+        allowNestedQuotes={rest.allowNestedQuotes}
+      />
+    )
+  }
+
+  return (
+    <PostPlaceholderText>
+      <Trans>Deleted</Trans>
+    </PostPlaceholderText>
+  )
+}
+
 /*
  * Nests parent `Embed` component and therefore must live in this file to avoid
  * circular imports.

src/screens/PostThread/components/ThreadItemAnchor.tsx

@@ -553,7 +553,7 @@ function ExpandedPostDetails({
     () =>
       Boolean(
         langPrefs.primaryLanguage &&
-          !isPostInLanguage(post, [langPrefs.primaryLanguage]),
+        !isPostInLanguage(post, [langPrefs.primaryLanguage]),
       ),
     [post, langPrefs.primaryLanguage],
   )
@@ -688,7 +688,7 @@ function BackdatedPostIndicator({post}: {post: AppBskyFeedDefs.PostView}) {
               <RNText style={[a.font_semi_bold]}>
                 {niceDate(i18n, createdAt)}
               </RNText>
-              , but was first seen by Bluesky on{' '}
+              , but was first seen by Blacksky on{' '}
               <RNText style={[a.font_semi_bold]}>
                 {niceDate(i18n, indexedAt)}
               </RNText>
@@ -697,7 +697,7 @@ function BackdatedPostIndicator({post}: {post: AppBskyFeedDefs.PostView}) {
           </Prompt.DescriptionText>
           <Prompt.DescriptionText>
             <Trans>
-              Bluesky cannot confirm the authenticity of the claimed date.
+              Blacksky cannot confirm the authenticity of the claimed date.
             </Trans>
           </Prompt.DescriptionText>
         </Prompt.Content>

src/state/queries/embed-fallback.ts

@@ -0,0 +1,21 @@
+import {useQuery, useQueryClient} from '@tanstack/react-query'
+
+import {STALE} from '#/state/queries'
+import {buildSyntheticEmbedViewRecord} from './microcosm-fallback'
+
+const RQKEY_ROOT = 'embed-fallback'
+export const RQKEY = (uri: string) => [RQKEY_ROOT, uri]
+
+export function useEmbedFallback({uri}: {uri: string}) {
+  const queryClient = useQueryClient()
+
+  return useQuery({
+    staleTime: STALE.HOURS.ONE,
+    queryKey: RQKEY(uri),
+    async queryFn() {
+      const result = await buildSyntheticEmbedViewRecord(queryClient, uri)
+      return result ?? undefined
+    },
+    enabled: !!uri,
+  })
+}