feat(files): download from anywhere — a link box, a pasted link, the palette; the running downloads in a tray

- Files toolbar link box (paste button, Enter); a lone http(s) link pasted onto any page opens the one
  app-wide download dialog, which now names the link; the palette's "Download from a link…" focuses
  the box on its history entry.
- The download tray, bottom right on every page: what waits, runs, is paused or failed (reason +
  Retry, the queue's right-click / "…" menu), and what finished in this tab as "Done · Open" until
  closed; folds to a pill (per-account pref); closed, it stays shut — across a reload — until the
  work changes or something finishes. Back to top steps up over it, the page end keeps clear.
- A finish is announced once: "Downloaded: …", whether a phone plays it, Copy link + Open (toasts
  and notices may carry a second action).
- The inbox's ready notice opens the file in its folder: download_done carries job_id + folder_id.
- GET /api/downloads is the queue only (in flight, failed, finished in the last 10 minutes), with
  each row's source key.

backend/app/routes/downloads.py

@@ -30,7 +30,7 @@ from app.downloads import edit as editmod
 from app.downloads import links as linksmod
 from app.downloads import quota, service, storage
 from app.downloads import urlguard
-from app.downloads.status import NOT_REFETCHABLE, JobStatus
+from app.downloads.status import FINISHED, NOT_REFETCHABLE, JobStatus
 from app.models import (
     DownloadJob,
     DownloadLink,
@@ -58,6 +58,7 @@ from app.routes.files import (
     quota_detail,
     serialize,
     serialize_job,
+    source_keys,
 )
 from app.security import hash_password
 from app.userscope import is_messageable_user, messageable_clauses
@@ -396,12 +397,22 @@ def enqueue_clip(
     return serialize_job(db, job)
 
 
+# How long a finished job stays in the queue: the tray polls it from every page and must see a job
+# turn done (its "Done · Open" row and the done notice) — the finished file itself is the library's.
+QUEUE_RECENT = timedelta(minutes=10)
+
+
 @router.get("")
 def list_downloads(user: User = Depends(current_user), db: Session = Depends(get_db)) -> list[dict]:
+    """The queue: what is waiting, running, paused or failed, and what finished a moment ago."""
+    recent = datetime.now(timezone.utc) - QUEUE_RECENT
     jobs = (
         db.execute(
             select(DownloadJob)
-            .where(DownloadJob.user_id == user.id)
+            .where(
+                DownloadJob.user_id == user.id,
+                DownloadJob.status.not_in(FINISHED) | (DownloadJob.updated_at >= recent),
+            )
             .order_by(DownloadJob.created_at.desc(), DownloadJob.id.desc())
             .limit(MAX_LIST)
         )
@@ -410,10 +421,12 @@ def list_downloads(user: User = Depends(current_user), db: Session = Depends(get
     )
     assets = assets_for(db, jobs)
     positions = positions_for(db, user, jobs)
+    sources = source_keys(db, jobs)
     return [
         {
             **serialize(j, assets.get(j.asset_id) if j.asset_id is not None else None),
             "position_seconds": positions.get(j.id, 0),
+            "source_key": sources[j.id],
         }
         for j in jobs
     ]

backend/app/routes/files.py

@@ -556,7 +556,7 @@ def list_files(
     assets = assets_for(db, jobs)
     positions = positions_for(db, user, jobs)
     shared_at = _shared_at(db, user, jobs) if shared else {}
-    sources = _source_keys(db, jobs)
+    sources = source_keys(db, jobs)
     return [
         {
             **serialize(j, assets.get(j.asset_id) if j.asset_id is not None else None),
@@ -569,9 +569,9 @@ def list_files(
     ]
 
 
-def _source_keys(db: Session, jobs: Sequence[DownloadJob]) -> dict[int, str]:
-    """Where each file came from (its source folder's key), for the list's Source column and the
-    "back to its source folder" move: a file in a source folder has its folder's key; one moved into
+def source_keys(db: Session, jobs: Sequence[DownloadJob]) -> dict[int, str]:
+    """Where each file came from (its source folder's key), for the list's Source column, the
+    "back to its source folder" move and the download tray's site: a file in a source folder has its folder's key; one moved into
     an own folder (or someone else's, shared) is traced back by `folders.source_key_for`."""
     ids = {j.folder_id for j in jobs if j.folder_id is not None}
     by_id = (