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>

alembic/versions/0085_wip_title_tagging.py

@@ -0,0 +1,35 @@
+"""title-based WIP auto-tagging (task #1458) — ImportSettings toggle
+
+ImportSettings gains wip_title_tagging_enabled (ON by default): when a freshly
+imported post's title explicitly declares work-in-progress ("WIP" / "work in
+progress"), the importer applies the `wip` system tag to its images. No new
+table — the tag itself is the seeded `wip` system tag (migration 0075) and the
+application reuses image_tag with source='wip_title'.
+
+Revision ID: 0085
+Revises: 0084
+Create Date: 2026-07-12
+"""
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = "0085"
+down_revision: Union[str, None] = "0084"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "import_settings",
+        sa.Column(
+            "wip_title_tagging_enabled", sa.Boolean(), nullable=False,
+            server_default=sa.text("true"),
+        ),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("import_settings", "wip_title_tagging_enabled")