fix(scan): auto-finalize empty scans + system_stats picks running batch with actual work

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/app/api/settings.py

@@ -141,11 +141,23 @@ async def system_stats():
         ).all()
         integrity_counts = {row[0]: row[1] for row in integrity_rows}
 
-        # Active batch (most recent running)
+        # Active batch = running batch that still has outstanding work.
+        # Plain "most recent running" picks a freshly-created scan that
+        # enqueued zero new files and hides the older batch that's
+        # actually being processed; the EXISTS clause filters those
+        # empty batches out.
         active_batch_row = (
             await session.execute(
                 select(ImportBatch)
-                .where(ImportBatch.status == "running")
+                .where(
+                    ImportBatch.status == "running",
+                    select(ImportTask.id)
+                    .where(
+                        ImportTask.batch_id == ImportBatch.id,
+                        ImportTask.status.in_(["pending", "queued", "processing"]),
+                    )
+                    .exists(),
+                )
                 .order_by(ImportBatch.started_at.desc())
                 .limit(1)
             )

backend/app/tasks/scan.py

@@ -95,6 +95,15 @@ def scan_directory(self, triggered_by: str = "manual",
             files_seen += 1
 
         batch.total_files = files_seen
+        # If the walk enqueued nothing (every file was already on a
+        # non-failed ImportTask from a prior scan), there's no
+        # import_media_file message that would ever flip this batch to
+        # 'complete' — finalize it now so the active-batch query in
+        # /api/system/stats doesn't get stuck reporting all-zero
+        # counters from an empty scan.
+        if files_seen == 0:
+            batch.status = "complete"
+            batch.finished_at = datetime.now(UTC)
         session.commit()
 
         # Now enqueue import_media_file for each pending task.