Add guided tours and unify left-to-right hall wall hang.

Visitors walk published tours in a 3D hall with stop notes; curators edit drafts via Tour editor. All galleries (artist, movement, tour) place the first work left of the entrance view and the last on the right.

Co-authored-by: Cursor <cursoragent@cursor.com>

db/migrate-tours.sql

@@ -0,0 +1,40 @@
+-- Guided tours: curated ordered stops with per-painting text.
+
+CREATE TABLE IF NOT EXISTS tours (
+  id SERIAL PRIMARY KEY,
+  title VARCHAR(200) NOT NULL,
+  description TEXT NOT NULL DEFAULT '',
+  status VARCHAR(20) NOT NULL DEFAULT 'draft'
+    CHECK (status IN ('draft', 'published')),
+  cover_painting_id INTEGER REFERENCES paintings(id) ON DELETE SET NULL,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+  updated_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX IF NOT EXISTS tours_status_idx ON tours (status);
+CREATE INDEX IF NOT EXISTS tours_updated_at_idx ON tours (updated_at DESC);
+
+CREATE TABLE IF NOT EXISTS tour_stops (
+  id SERIAL PRIMARY KEY,
+  tour_id INTEGER NOT NULL REFERENCES tours(id) ON DELETE CASCADE,
+  painting_id INTEGER NOT NULL REFERENCES paintings(id) ON DELETE CASCADE,
+  sort_order INTEGER NOT NULL DEFAULT 0,
+  body TEXT NOT NULL DEFAULT '',
+  UNIQUE (tour_id, painting_id)
+);
+
+CREATE INDEX IF NOT EXISTS tour_stops_tour_idx ON tour_stops (tour_id, sort_order);
+CREATE INDEX IF NOT EXISTS tour_stops_painting_idx ON tour_stops (painting_id);
+
+CREATE OR REPLACE FUNCTION tours_touch_updated_at()
+RETURNS TRIGGER AS $$
+BEGIN
+  NEW.updated_at = now();
+  RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+DROP TRIGGER IF EXISTS tours_updated_at ON tours;
+CREATE TRIGGER tours_updated_at
+  BEFORE UPDATE ON tours
+  FOR EACH ROW EXECUTE PROCEDURE tours_touch_updated_at();