fix(e12): close what round one broke, and revert two fixes that overreached

Round two of the review loop, on round one's own diff. Two of its findings were
regressions the fixes themselves introduced, which is exactly what the loop is for:

**A per-user refusal was writing onto a shared row.** MediaAssets are deduped across
users, and the generic failure handler puts the message on the asset — right for an
upstream failure, wrong for "your storage is full". Two users queuing the same video share
one asset, so the first user hitting their cap failed the second user's job with the first
one's private reason, telling someone with an empty library to free up space. The refusal
now raises `_OwnerRefused`, caught separately: the job fails, the asset goes back to
`pending` for whoever else holds it. Pinned by a test that drives `_download` directly —
the refusal happens before extraction, so nothing needs stubbing.

**The restore scripts restarted the app, undoing the restore.** `docker compose start`
re-runs the container command, and that runs `alembic upgrade head` — so on the rollback
path this documents as recommended (restore the dump, THEN pin the older tag) the newer
image immediately re-applied the migrations the restore had just undone, and on a FAILED
restore it put the app back on a half-restored schema. Both are the opposite of why the
stop was added. Nothing is restarted automatically now; the scripts say what to run and
when, and the docs' snippets say the same.

**Reverted rather than patched:** the OnboardingWizard toast (the wizard already renders
that failure inline, next to a Retry button — three recoveries for one failure), and
`useVerifyEntry`'s "each new link clears the other". The latter blanked the signed-out
card's only banner, where nothing renders the reset flag to replace it. The two states are
independent again; what changes is that `dismiss` peels ONE layer, which is what the
original finding was actually about.

Also: `Stats` uses the YouTube helper rather than the bare one, so the route's English 403
detail no longer beats the translated fallback under a Hungarian UI; `urlparse` guarded
alongside `.port` (an unclosed bracket raised just as late), the reason renamed `malformed`
since "bad port" misdescribes it; three docstrings narrowed to what the code actually does
(the worker's byte check is per-job, not an aggregate ledger, and not on the edit path;
the redirect residual leaks a reachability oracle, which the note had denied; the
invalidation helper does not cover suspend); the pasted Windows recipe wrapped so `throw`
can stop it; the bash one-liner's failure branch no longer exits 0; and the tests that were
missing for the round-one fixes — the account panel's error paths, the invalidation set,
and the shared-asset case above.

Gate green: vitest 685, pytest 950.

backend/tests/test_download_limits.py

@@ -10,7 +10,8 @@ Uses the `db` fixture (real Postgres) — skipped when no database is reachable.
 its OWN session, so every test COMMITS its setup before calling it.
 """
 
-from app.downloads import quota
+from app.config import settings
+from app.downloads import pipeline, quota
 from app.models import DownloadJob, DownloadQuota, MediaAsset, User
 from app.worker import _claim_job
 
@@ -228,3 +229,45 @@ def test_remaining_bytes_is_zero_once_the_cap_is_met(db):
     _job(db, u.id, queue_pos=0, status="done", asset_id=a.id)
     db.flush()
     assert quota.remaining_bytes(db, u.id) == 0
+
+
+def test_a_refusal_for_one_user_does_not_poison_the_shared_asset(db, monkeypatch, tmp_path):
+    """A user at their cap fails their own job, and another user's queued job for the same video
+    still downloads.
+
+    MediaAssets are deduped across users, and the generic failure handler writes the message onto
+    that shared row — correct for an upstream failure, wrong for "YOUR storage is full", which
+    `worker._process_job` would then hand verbatim to someone with an empty library.
+    """
+    monkeypatch.setattr(settings, "download_root", str(tmp_path))
+    over, other = User(email="over@example.com"), User(email="other@example.com")
+    db.add_all([over, other])
+    db.flush()
+    db.add(
+        DownloadQuota(
+            user_id=over.id, max_bytes=1000, max_concurrent=2, max_jobs=100, unlimited=False
+        )
+    )
+    full = _sized_asset(db, 1500, "already-held")
+    _job(db, over.id, queue_pos=0, status="done", asset_id=full.id)
+
+    shared = MediaAsset(
+        source_kind="youtube", source_ref="x" * 11, format_sig="s", status="pending", ref_count=2
+    )
+    db.add(shared)
+    db.flush()
+    mine = _job(db, over.id, queue_pos=1, status="running", asset_id=shared.id)
+    theirs = _job(db, other.id, queue_pos=2, asset_id=shared.id)
+    db.commit()
+
+    # The refusal happens before extraction, so nothing needs stubbing — if it ever stops happening
+    # first, this test starts reaching the network, which is its own signal.
+    pipeline._download(mine.id, shared.id, "youtube", "x" * 11, {}, over.id)
+
+    db.expire_all()
+    assert db.get(DownloadJob, mine.id).status == "error"
+    assert db.get(DownloadJob, mine.id).error_code == "quota_exceeded"
+    # The asset is released, NOT marked error — otherwise the next line's job inherits the refusal.
+    assert db.get(MediaAsset, shared.id).status == "pending"
+    assert db.get(MediaAsset, shared.id).error is None
+    assert db.get(DownloadJob, theirs.id).status == "queued"