feat(wip): soft title tier — sketch/doodle vocab + ring-loud audit (#1474)

Extends WIP title-tagging to lower-precision cues (sketch/doodle/scribble) safely.

- wip_title.py: soft matcher (word-anchored; sketchbook/kadoodle don't trip it);
  WIP_TITLE_SOFT_SOURCE + soft SQL prefilter; apply_wip_image_tags takes a source arg.
- training_data._AUTO_SOURCES += 'wip_title_soft' → the soft tier is PROVISIONAL and
  never trains the wip head (a finished "sketch" can't pollute it). Only the hard
  tier (wip_title) + manual train.
- ImportSettings.wip_soft_title_tagging_enabled (OFF by default, opt-in). Migration 0087.
- importer: hard tier wins, soft is the fallback (source wip_title_soft).
- backfill: refactored into a shared _backfill_wip_tier; hard always, soft when enabled.
- heads.soft_wip_conflict_audit + daily beat: score soft-tagged images against content
  heads, flag ring-loud ones (PresentationReview mode=process) for the review strip —
  the operator's "measure if they got falsely tagged" safety.
- api settings toggle; ImportFiltersForm soft toggle.
- tests: soft matcher pos/neg; soft source not a training positive; audit flags
  ring-loud + spares quiet.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/test_wip_title.py

@@ -8,7 +8,7 @@ negative cases (substrings like ``swipe`` / ``wiped``) are the load-bearing ones
 """
 import pytest
 
-from backend.app.services.wip_title import matches_wip_title
+from backend.app.services.wip_title import matches_soft_wip_title, matches_wip_title
 
 
 @pytest.mark.parametrize("title", [
@@ -44,6 +44,33 @@ def test_matches_positive(title):
     "finished at last",
     "Kawips diner",                 # 'wip' mid-word
     "swipright",
+    "quick sketch of Nami",         # soft cue — NOT a HARD WIP match
 ])
 def test_matches_negative(title):
     assert matches_wip_title(title) is False
+
+
+@pytest.mark.parametrize("title", [
+    "quick sketch",
+    "Nami sketch",
+    "morning doodle",
+    "some doodles",
+    "sketches from today",
+    "a little scribble",
+    "SKETCH",
+])
+def test_soft_matches_positive(title):
+    assert matches_soft_wip_title(title) is True
+
+
+@pytest.mark.parametrize("title", [
+    None,
+    "",
+    "sketchbook tour",              # 'sketch' inside sketchbook — must NOT match
+    "kadoodle mascot",              # 'doodle' mid-word
+    "the final piece",
+    "WIP",                          # a HARD cue is not a SOFT cue
+    "prescribed colours",           # 'scrib' inside prescribed — must NOT match
+])
+def test_soft_matches_negative(title):
+    assert matches_soft_wip_title(title) is False