fix(download): dispatch archive/non-media in attach_in_place; reshuffle showcase on mount

attach_in_place mirrored only the media flow, so gallery-dl-downloaded
zips/PDFs/audio bounced back as `skipped+invalid_image`, which
download_service counted as an ingest error and flipped runs to
status="error" despite N successful image attaches. Lustria patreon
event #38998 (21 images + 1 OST zip) went red for exactly this reason.

Now attach_in_place dispatches the same way as import_one: archives →
_import_archive (extracts media members, captures archive as
PostAttachment), non-media → _capture_attachment. Download_service
accepts the new `attached` result and treats non-duplicate skips as
soft skips, not ingest errors.

Also: ShowcaseView always loadInitial() on mount, not just when the
store is empty — Pinia persists across navigations and operator wants
a fresh shuffle every time the showcase loads.

backend/app/services/importer.py

@@ -650,16 +650,34 @@ class Importer:
         them through. The sidecar JSON gallery-dl emits next to each
         downloaded file is read by `_apply_sidecar` via `find_sidecar`.
 
+        File-type dispatch parity with `import_one` (FC-2d-iii): zips,
+        PDFs, audio etc. become PostAttachments; archives are extracted.
+        Without this dispatch, gallery-dl-downloaded non-media bounced
+        back as `skipped+invalid_image`, which DownloadService counted
+        as an ingest error and flipped otherwise-successful runs to
+        status="error". Operator-flagged 2026-06-02 after a Lustria
+        patreon run with a 94MB OST zip went red despite 21 successful
+        image attaches.
+
         Caller's responsibilities after this returns:
           - duplicate_hash / duplicate_phash skip → delete the on-disk file
           - superseded → file stays where it is (now canonical)
           - imported → file stays where it is
+          - attached → the file's been copied into the attachments store;
+            caller may delete the on-disk original (mirrors duplicate_hash)
           - failed → file untouched; caller decides
         """
-        if not is_supported(path):
+        if path.suffix.lower() == ".json":
             return ImportResult(
                 status="skipped", skip_reason=SkipReason.invalid_image,
-                error=f"unsupported extension {path.suffix}",
+                error="sidecar json is metadata, not content",
+            )
+        if is_archive(path):
+            return self._import_archive(path)
+        if not is_supported(path):
+            post = self._post_for_sidecar(path, artist) if artist else None
+            return self._capture_attachment(
+                path, post=post, artist=artist, resolved=True,
             )
 
         # Format / dimension / transparency filters (mirror _import_media).