fix(import): split archive imports into their own task + budget; archive-aware recovery sweeps

Operator-flagged 2026-05-28: import_media_file on target 1645019 hit
SoftTimeLimitExceeded at exactly 5.0 min. Their diagnosis was correct —
the timeout covered the WHOLE archive, not per object. Importer._import_archive
(importer.py:409) runs the full per-member pipeline (sha256 + pHash +
dedup query + copy + provenance) for EVERY media member inline, all
under import_media_file's single 300s soft limit. A single media file
is sub-second; a multi-hundred-member archive blows the budget. They
shared one task name and one timeout.

**Split archive into its own task**

- New `import_archive_file` task: same body as import_media_file
  (dispatch is by file-kind inside Importer.import_one) but
  soft=30min / hard=35min. Shared `_run_import_task` helper holds the
  flip-to-processing + resilience-contract wrapper; both tasks call it.
- New `enqueue_import(task_id, task_type)` router — single source of
  truth for media-vs-archive dispatch. Used by all three enqueue sites:
  scan_directory, /api/import/retry-failed, recover_interrupted_tasks.
- scan_directory now sets ImportTask.task_type = "archive" when
  is_archive(entry) (the model field already existed, anticipating
  this; scan was hardcoding "media").
- import_archive_file routes to the existing 'import' queue via the
  task_routes `import_file.*` wildcard — no worker config change.

**Archive-aware recovery sweeps**

Both sweeps would otherwise preempt a legitimately-running archive:

- recover_interrupted_tasks (ImportTask 'processing' sweep): now
  task-type-aware. Media stays at STUCK_THRESHOLD_MINUTES (5); archives
  get ARCHIVE_STUCK_THRESHOLD_MINUTES (40 = 5-min buffer past the
  35-min hard limit). Single UPDATE with an OR predicate over the two
  (task_type, cutoff) pairs; requeue routes via enqueue_import.
- recover_stalled_task_runs (TaskRun 'running' sweep): now supports
  per-task-name overrides (TASK_STUCK_THRESHOLD_MINUTES) layered above
  the per-queue overrides added for ml. import_archive_file gets 40 min
  while the 'import' queue stays at the 5-min default for single-file
  imports. Precedence: task_name → queue → default, each pass excluding
  rows claimed by a higher-precedence pass so every row is touched once.

**Tests**

- test_import_archive_file_registered
- test_recover_stalled_task_runs_archive_task_uses_longer_threshold —
  pins that a 10-min archive task-run survives, a 50-min one is flagged,
  and a same-queue 10-min media import is flagged at the default.
- _make_task_run gains queue= + task_name= params.

After deploy: archive imports get a 30-min budget and aren't preempted
by either sweep; single-file imports keep their tight 5-min detection.

backend/app/api/import_admin.py

@@ -114,18 +114,18 @@ async def retry_failed():
                 status="queued", error=None,
                 started_at=None, finished_at=None,
             )
-            .returning(ImportTask.id)
+            .returning(ImportTask.id, ImportTask.task_type)
         )
-        failed_ids = [row[0] for row in result.all()]
-        if not failed_ids:
+        failed = result.all()
+        if not failed:
             return jsonify({"retried": 0})
         await session.commit()
 
-    from ..tasks.import_file import import_media_file
-    for tid in failed_ids:
-        import_media_file.delay(tid)
+    from ..tasks.import_file import enqueue_import
+    for tid, task_type in failed:
+        enqueue_import(tid, task_type)
 
-    return jsonify({"retried": len(failed_ids)})
+    return jsonify({"retried": len(failed)})
 
 
 @import_admin_bp.route("/clear-stuck", methods=["POST"])