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>

backend/app/services/importer.py

@@ -43,6 +43,7 @@ from ..utils.phash import compute_phash, find_similar
 from ..utils.sidecar import find_sidecar, parse_sidecar
 from ..utils.slug import slugify
 from .archive_extractor import extract_archive, is_archive
+from .wip_title import apply_wip_image_tags, matches_wip_title, resolve_wip_tag_id
 from .attachment_store import AttachmentStore
 from .audits import single_color
 from .link_extract import extract_external_links
@@ -50,6 +51,10 @@ from .thumbnailer import Thumbnailer
 
 log = logging.getLogger(__name__)
 
+# Sentinel for the lazily-resolved wip tag id (distinguishes "not resolved yet"
+# from a genuine None = tag absent, so absence is cached and not re-queried).
+_UNSET = object()
+
 
 class SkipReason(StrEnum):
     too_small = "too_small"
@@ -183,6 +188,10 @@ class Importer:
         # invalidated mid-Importer (Importer instances are per-task /
         # per-archive-import so cross-instance staleness is harmless).
         self._phash_candidates: list[tuple] | None = None
+        # Lazily-resolved `wip` system tag id for title-based WIP auto-tagging
+        # (task #1458). Sentinel _UNSET so a genuine None (tag absent) is cached
+        # and not re-queried per media. Importer is per-task, so this can't stale.
+        self._wip_tag_id: int | None = _UNSET
 
     def _phash_candidates_cache(self) -> list[tuple]:
         """Cached `(phash, width, height, id)` rows from image_record.
@@ -933,6 +942,10 @@ class Importer:
         # Thumbnail is queued separately by the calling task; the importer
         # does not generate thumbnails inline so the import queue stays moving.
 
+        # Title-based WIP auto-tag (task #1458): fresh import only, after the
+        # sidecar has linked the post so record.primary_post_id / its title exist.
+        self._maybe_apply_wip_title(record)
+
         self.session.commit()
         return ImportResult(status="imported", image_id=record.id)
 
@@ -976,6 +989,36 @@ class Importer:
         self.session.commit()
         return ImportResult(status="refreshed", image_id=existing.id)
 
+    def _maybe_apply_wip_title(self, record: ImageRecord) -> None:
+        """Auto-apply the `wip` system tag to a FRESHLY-imported image when its
+        primary post's TITLE explicitly declares work-in-progress (task #1458 —
+        the artist's own "WIP" / "work in progress" label).
+
+        Called ONLY from the two new-record paths (never deep-scan / supersede),
+        so a manually-removed WIP tag is never re-applied by a routine re-scan —
+        removal sticks. The existing catalogue is covered separately by the
+        operator-triggered backfill sweep. Gated by the settings toggle, and
+        best-effort: any failure is logged, never allowed to fail the import."""
+        if not self.settings.wip_title_tagging_enabled:
+            return
+        if record.primary_post_id is None:
+            return
+        try:
+            title = self.session.execute(
+                select(Post.post_title).where(Post.id == record.primary_post_id)
+            ).scalar_one_or_none()
+            if not matches_wip_title(title):
+                return
+            if self._wip_tag_id is _UNSET:
+                self._wip_tag_id = resolve_wip_tag_id(self.session)
+            if self._wip_tag_id is None:
+                return
+            apply_wip_image_tags(self.session, [record.id], self._wip_tag_id)
+        except Exception as exc:  # noqa: BLE001 — a tag must never fail an import
+            log.warning(
+                "wip-title auto-tag failed for image %s: %s", record.id, exc
+            )
+
     def _apply_post_fields(self, post: Post, sd) -> None:
         """Write a parsed sidecar's post-level fields onto a Post — the SINGLE
         predicate shared by BOTH ingest paths: the per-media path (_apply_sidecar)
@@ -1253,6 +1296,10 @@ class Importer:
         # per-post Source row.
         self._apply_sidecar(record, path, artist, explicit_source=source)
 
+        # Title-based WIP auto-tag (task #1458): fresh import only, see the
+        # matching call in _import_media.
+        self._maybe_apply_wip_title(record)
+
         self.session.commit()
         return ImportResult(status="imported", image_id=record.id)