feat(tagging): skipped tags hide matching suggestions (#431)

A Skipped tags list in System > Auto-tagging (D202) hides every suggested
tag whose words contain an entry's words, on every suggestion path
(Tag image, Auto-tag selected, the System batch, the legacy single and
batch routes), before the limit. Jobs snapshot the list at their start.
A read-only preview route counts what a list hides among the library's
tags and the downloaded WD14 label lists. The draft store compares list
and object drafts by value (sameDraft).

tests/fixtures/legacy_contract_snapshot.json

@@ -105,6 +105,7 @@
     "POST /prompt_manager/autotag/batch/preview",
     "POST /prompt_manager/autotag/download/{model_type}",
     "POST /prompt_manager/autotag/single",
+    "POST /prompt_manager/autotag/skipped-tags/preview",
     "POST /prompt_manager/autotag/start",
     "POST /prompt_manager/autotag/unload",
     "POST /prompt_manager/bulk/category",
@@ -188,6 +189,7 @@
     "settings.autotag_existing",
     "settings.autotag_general_threshold",
     "settings.autotag_model_type",
+    "settings.autotag_skipped_tags",
     "settings.autotag_suggestion_limit",
     "settings.autotag_template",
     "settings.cpu_count",