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.

tests/test_importer_attach_in_place.py

@@ -159,3 +159,30 @@ def test_attach_in_place_invalid_image_returns_skipped(importer):
     result = importer.attach_in_place(bad)
     assert result.status == "skipped"
     assert result.skip_reason.value == "invalid_image"
+
+
+def test_attach_in_place_non_media_routes_to_attachment(importer, db_sync):
+    """FC-2d-iii dispatch parity for the download path. A non-media file
+    (.pdf, .txt etc.) downloaded by gallery-dl must become a PostAttachment,
+    not bounce back as `skipped+invalid_image` — the latter flipped
+    otherwise-successful runs to status="error" downstream. Operator-flagged
+    2026-06-02 (Lustria patreon OST zip)."""
+    from backend.app.models import PostAttachment
+
+    images_root = importer.images_root
+    artist = Artist(name="Gus", slug="gus")
+    db_sync.add(artist)
+    db_sync.flush()
+
+    txt = images_root / "gus" / "patreon" / "post" / "notes.txt"
+    txt.parent.mkdir(parents=True, exist_ok=True)
+    txt.write_bytes(b"some non-media payload that the importer should preserve")
+
+    result = importer.attach_in_place(txt, artist=artist)
+    assert result.status == "attached"
+
+    row = db_sync.execute(
+        select(PostAttachment).where(PostAttachment.original_filename == "notes.txt")
+    ).scalar_one()
+    assert row.ext == ".txt"
+    assert row.artist_id == artist.id