fix(downloads): a converted upload too big says so, and a suspended owner's waiting rebuild is not "preparing"

- A converted upload over the space left (not zero) fails with CONVERTED_TOO_BIG_MESSAGE, not
  "storage is full"; it classifies as quota_exceeded by the phrase it shares with the clip's.
- The public watch page says "preparing" only for a job a worker will take: a suspended owner's
  queued job waits for as long as the suspension lasts, so the link says the video is gone, as
  for a paused rebuild.
- The worker's claim docstring names the restart case: a running job put back in the queue waits.

backend/app/routes/public.py

@@ -17,7 +17,7 @@ from app.db import get_db
 from app.downloads import links as linksmod
 from app.downloads import storage
 from app.downloads.status import JobStatus
-from app.models import DownloadJob, DownloadLink, MediaAsset
+from app.models import DownloadJob, DownloadLink, MediaAsset, User
 from app.ratelimit import RateLimiter, client_key
 from app.security import verify_password
 from app.refusal import refused
@@ -44,6 +44,17 @@ def _link_or_404(db: Session, token: str) -> DownloadLink:
     return link
 
 
+def _being_made(db: Session, job: DownloadJob) -> bool:
+    """The job is running, or queued for a worker that will take it: the worker leaves a suspended
+    owner's queued jobs where they are (`worker._claim_job`), as long as the suspension lasts."""
+    if job.status == JobStatus.RUNNING:
+        return True
+    if job.status != JobStatus.QUEUED:
+        return False
+    owner = db.get(User, job.user_id)
+    return owner is not None and not owner.is_suspended
+
+
 def _ready_target(db: Session, link: DownloadLink) -> tuple[DownloadJob, MediaAsset]:
     job = db.get(DownloadJob, link.job_id)
     asset = db.get(MediaAsset, job.asset_id) if job and job.asset_id else None
@@ -51,7 +62,7 @@ def _ready_target(db: Session, link: DownloadLink) -> tuple[DownloadJob, MediaAs
         job is not None
         and asset is not None
         and asset.status in ("pending", "downloading")
-        and job.status in (JobStatus.QUEUED, JobStatus.RUNNING)
+        and _being_made(db, job)
     ):
         # Being (re)made — a re-download, or a conversion — so the link works again once it is ready:
         # its own reason, so the page can say "try again shortly" rather than "this link is gone".