feat(tagging): title-based WIP auto-tagging (#1458)

Auto-apply the `wip` system tag to posts whose TITLE explicitly declares
work-in-progress ("WIP" / "work in progress") — a deterministic, high-precision
complement to the image-based ML `wip` head. WIP images are excluded from the
Explore/gallery browse, so honouring the artist's own label keeps unfinished
pieces out of the main browse.

- services/wip_title.py: precision-first token-anchored matcher (swipe/wiped
  never trip it) + sync apply helpers (source='wip_title', ON CONFLICT DO
  NOTHING, chunked under the psycopg param ceiling).
- importer: live hook on FRESH import only (never on deep-scan/supersede), so a
  manually-removed WIP tag is never re-applied by a routine re-scan.
- maintenance.backfill_wip_title_tags: operator-triggered back-catalogue sweep
  (coarse SQL prefilter + regex confirm, keyset-paginated). Deliberately NOT a
  beat — a periodic re-run would silently undo manual removals.
- ImportSettings.wip_title_tagging_enabled (default ON, migration 0085) gating
  the live hook; GET/PATCH + POST /settings/wip-title/scan.
- Settings UI: toggle + "Scan existing posts" button.
- Tests: pure matcher unit tests + integration (apply idempotency, backfill
  precision).

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

frontend/src/components/settings/ImportFiltersForm.vue

@@ -79,6 +79,35 @@
         </v-col>
       </v-row>
 
+      <v-divider class="my-5" />
+
+      <!-- Title-based WIP auto-tagging (task #1458). The switch gates the LIVE
+           import hook; the button runs the one-off back-catalogue scan (an
+           explicit action — it is deliberately not a scheduled sweep so it can't
+           silently re-apply a WIP tag you removed by hand). -->
+      <div class="fc-wip">
+        <div class="fc-wip__title">WIP auto-tagging</div>
+        <v-switch
+          v-model="local.wip_title_tagging_enabled"
+          label="Tag work-in-progress from post titles"
+          density="compact" hide-details color="primary" @change="save"
+        />
+        <div class="fc-help mb-3">
+          When a post's title says <strong>“WIP”</strong> or
+          <strong>“work in progress”</strong>, new imports get the
+          <code>wip</code> tag automatically — keeping unfinished pieces out of
+          the Explore browse. Applies to new imports; run the scan below to catch
+          posts already in your library.
+        </div>
+        <v-btn
+          variant="tonal" color="primary" size="small"
+          :loading="store.wipScanBusy" prepend-icon="mdi-magnify"
+          @click="store.scanWipTitles()"
+        >
+          Scan existing posts for WIP titles
+        </v-btn>
+      </div>
+
       <v-alert v-if="store.settingsError" type="error" variant="tonal" class="mt-2" closable>
         {{ store.settingsError }}
       </v-alert>
@@ -109,6 +138,7 @@ const local = reactive({
   skip_transparent: false, transparency_threshold: 0.9,
   skip_single_color: false, single_color_threshold: 0.95,
   phash_threshold: 10,
+  wip_title_tagging_enabled: true,
 })
 
 watch(() => store.settings, (s) => { if (s) Object.assign(local, s) }, { immediate: true })
@@ -124,11 +154,18 @@ async function save() {
   color: rgb(var(--v-theme-on-surface-variant));
   margin-top: 2px;
 }
-.fc-phash__title {
+.fc-phash__title,
+.fc-wip__title {
   font-size: 0.95rem;
   font-weight: 600;
   color: rgb(var(--v-theme-on-surface));
 }
+.fc-wip code {
+  font-size: 0.85em;
+  padding: 1px 4px;
+  border-radius: 3px;
+  background: rgb(var(--v-theme-surface-variant));
+}
 /* Headroom so the tick labels (Exact/Strict/Default/Loose) aren't clipped. */
 .fc-phash__slider { margin-bottom: 18px; }
 </style>