fix(tagging): Tag output images tags each image, not its prompt (#379, PR 1)

The native "Tag output images" job now runs the image-tags loop over every
still image the output folders list, linked or not: each image gets its own
model tags (at most "Suggestions per image") in its image tag set, and its
bytes are marked auto-tagged in a new media_image_autotags table. No prompt
tag or prompt text is written.

- database/autotag_schema.py: one forward-only WITHOUT ROWID table, optional
  in old backups, refused without the annotation group.
- add_image_tags/replace_image_tags take mark_autotagged; autotag_state and
  autotagged_locators read the marks through the one current-record rule.
- "Skip already tagged" skips images whose current bytes are marked, counted
  in a stat-only pre-pass; hand tags do not count.
- The review counts images and estimates the time (WD14 on CPU or CUDA).
- System > Auto-tagging review rows and copy, D134 and the Auto-tagging
  contract follow.

Part of #379

tests/test_database_backup.py

@@ -468,6 +468,7 @@ class TestRestoreFromFile(BackupTestCase):
 
     def test_restore_old_backup_without_annotations(self):
         tables = (
+            "media_image_autotags",
             "media_review_decisions",
             "media_review_items",
             "media_review_metadata",