fix(ebooks): persist bounded reconciliation cursor

migrations/sql/20260719173000_ebook_enrichment_reconcile_cursor.sql

@@ -0,0 +1,37 @@
+-- +goose NO TRANSACTION
+
+-- +goose Up
+CREATE TABLE IF NOT EXISTS ebook_enrichment_reconcile_cursors (
+    folder_id integer PRIMARY KEY REFERENCES media_folders(id) ON DELETE CASCADE,
+    after_first_seen_at timestamptz,
+    after_content_id text,
+    updated_at timestamptz NOT NULL DEFAULT now(),
+    CHECK ((after_first_seen_at IS NULL) = (after_content_id IS NULL))
+);
+
+-- A failed CREATE INDEX CONCURRENTLY can leave an invalid index that blocks an
+-- IF NOT EXISTS retry. Drop only that unusable artifact before rebuilding.
+-- +goose StatementBegin
+DO $$
+BEGIN
+    IF EXISTS (
+        SELECT 1
+        FROM pg_class c
+        JOIN pg_namespace n ON n.oid = c.relnamespace
+        JOIN pg_index i ON i.indexrelid = c.oid
+        WHERE n.nspname = 'public'
+          AND c.relname = 'idx_item_libraries_folder_enrichment_cursor'
+          AND NOT i.indisvalid
+    ) THEN
+        DROP INDEX public.idx_item_libraries_folder_enrichment_cursor;
+    END IF;
+END;
+$$;
+-- +goose StatementEnd
+
+CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_item_libraries_folder_enrichment_cursor
+    ON public.media_item_libraries (media_folder_id, first_seen_at DESC, content_id);
+
+-- +goose Down
+DROP INDEX CONCURRENTLY IF EXISTS idx_item_libraries_folder_enrichment_cursor;
+DROP TABLE IF EXISTS ebook_enrichment_reconcile_cursors;