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>

frontend/src/components/settings/ImportFiltersForm.vue

@@ -99,6 +99,17 @@
           the Explore browse. Applies to new imports; run the scan below to catch
           posts already in your library.
         </div>
+        <v-switch
+          v-model="local.wip_soft_title_tagging_enabled"
+          label="Also tag “sketch” / “doodle” titles (lower precision)"
+          density="compact" hide-details color="primary" @change="save"
+        />
+        <div class="fc-help mb-3">
+          Extends the above to softer cues (<code>sketch</code>, <code>doodle</code>,
+          <code>scribble</code>). These stay <strong>visible</strong> and never train
+          the tagging model — a daily audit flags any that actually look like finished
+          art for review. Off by default.
+        </div>
         <v-btn
           variant="tonal" color="primary" size="small"
           :loading="store.wipScanBusy" prepend-icon="mdi-magnify"
@@ -139,6 +150,7 @@ const local = reactive({
   skip_single_color: false, single_color_threshold: 0.95,
   phash_threshold: 10,
   wip_title_tagging_enabled: true,
+  wip_soft_title_tagging_enabled: false,
 })
 
 watch(() => store.settings, (s) => { if (s) Object.assign(local, s) }, { immediate: true })