feat(dds): реализован слой dds для bookings

- Зачем:
  - подготовлен учебный Star Schema слой для перехода от ODS к аналитике и витринам.
- Что:
  - добавлены 21 SQL-файл для DDS (DDL/LOAD/DQ) с SCD1/SCD2 и фактом `fact_flight_sales`.
  - добавлены DAG `bookings_dds_ddl` и `bookings_to_gp_dds`, а также smoke-тесты структуры DAG.
  - обновлены `sql/ddl_gp.sql` и документация (`README`, `docs/*`, `db_schema`) под поток `stg -> ods -> dds`.
- Проверка:
  - make test.

sql/dds/dim_routes_dq.sql

@@ -0,0 +1,149 @@
+-- DQ для DDS dim_routes (SCD2).
+
+DO $$
+DECLARE
+    v_row_count BIGINT;
+    v_dup_sk BIGINT;
+    v_dup_current BIGINT;
+    v_overlap_count BIGINT;
+    v_missing_count BIGINT;
+    v_orphan_current BIGINT;
+    v_null_count BIGINT;
+BEGIN
+    -- Таблица не пуста.
+    SELECT COUNT(*)
+    INTO v_row_count
+    FROM dds.dim_routes;
+
+    IF v_row_count = 0 THEN
+        RAISE EXCEPTION 'DQ FAILED: dds.dim_routes пуста.';
+    END IF;
+
+    -- Нет дублей по SK.
+    SELECT COUNT(*) - COUNT(DISTINCT route_sk)
+    INTO v_dup_sk
+    FROM dds.dim_routes;
+
+    IF v_dup_sk <> 0 THEN
+        RAISE EXCEPTION
+            'DQ FAILED: в dds.dim_routes найдены дубликаты route_sk: %',
+            v_dup_sk;
+    END IF;
+
+    -- Корректность интервалов (valid_from <= valid_to для закрытых версий).
+    SELECT COUNT(*)
+    INTO v_null_count
+    FROM dds.dim_routes
+    WHERE valid_to IS NOT NULL
+        AND valid_from > valid_to;
+
+    IF v_null_count <> 0 THEN
+        RAISE EXCEPTION
+            'DQ FAILED: в dds.dim_routes найдены версии с valid_from > valid_to: %',
+            v_null_count;
+    END IF;
+
+    -- Нет перекрытий интервалов для одного route_bk.
+    SELECT COUNT(*)
+    INTO v_overlap_count
+    FROM (
+        SELECT 1
+        FROM dds.dim_routes AS d1
+        JOIN dds.dim_routes AS d2
+            ON d1.route_bk = d2.route_bk
+            AND d1.route_sk < d2.route_sk
+            AND d1.valid_from < COALESCE(d2.valid_to, DATE '9999-12-31')
+            AND d2.valid_from < COALESCE(d1.valid_to, DATE '9999-12-31')
+    ) AS overlap_rows;
+
+    IF v_overlap_count <> 0 THEN
+        RAISE EXCEPTION
+            'DQ FAILED: в dds.dim_routes найдены перекрытия SCD2-интервалов: %',
+            v_overlap_count;
+    END IF;
+
+    -- Не более одной текущей версии на route_bk.
+    SELECT COUNT(*)
+    INTO v_dup_current
+    FROM (
+        SELECT route_bk
+        FROM dds.dim_routes
+        WHERE valid_to IS NULL
+        GROUP BY route_bk
+        HAVING COUNT(*) > 1
+    ) AS d;
+
+    IF v_dup_current <> 0 THEN
+        RAISE EXCEPTION
+            'DQ FAILED: в dds.dim_routes найдены route_bk с > 1 текущей версией: %',
+            v_dup_current;
+    END IF;
+
+    -- Покрытие ODS: все route_no имеют хотя бы одну версию в DDS.
+    SELECT COUNT(*)
+    INTO v_missing_count
+    FROM (SELECT DISTINCT route_no FROM ods.routes) AS o
+    WHERE NOT EXISTS (
+        SELECT 1
+        FROM dds.dim_routes AS d
+        WHERE d.route_bk = o.route_no
+    );
+
+    IF v_missing_count <> 0 THEN
+        RAISE EXCEPTION
+            'DQ FAILED: в dds.dim_routes отсутствуют маршруты из ODS: %',
+            v_missing_count;
+    END IF;
+
+    -- Current-срез DDS не содержит route_bk, которых нет в ODS.
+    SELECT COUNT(*)
+    INTO v_orphan_current
+    FROM (
+        SELECT DISTINCT route_bk
+        FROM dds.dim_routes
+        WHERE valid_to IS NULL
+    ) AS d
+    WHERE NOT EXISTS (
+        SELECT 1
+        FROM ods.routes AS o
+        WHERE o.route_no = d.route_bk
+    );
+
+    IF v_orphan_current <> 0 THEN
+        RAISE EXCEPTION
+            'DQ FAILED: в current-срезе dds.dim_routes есть route_bk вне ODS: %',
+            v_orphan_current;
+    END IF;
+
+    -- Обязательные поля.
+    SELECT COUNT(*)
+    INTO v_null_count
+    FROM dds.dim_routes
+    WHERE route_sk IS NULL
+        OR route_bk IS NULL
+        OR route_bk = ''
+        OR departure_airport IS NULL
+        OR departure_airport = ''
+        OR arrival_airport IS NULL
+        OR arrival_airport = ''
+        OR airplane_code IS NULL
+        OR airplane_code = ''
+        OR hashdiff IS NULL
+        OR hashdiff = ''
+        OR valid_from IS NULL
+        OR created_at IS NULL
+        OR updated_at IS NULL
+        OR _load_id IS NULL
+        OR _load_id = ''
+        OR _load_ts IS NULL;
+
+    IF v_null_count <> 0 THEN
+        RAISE EXCEPTION
+            'DQ FAILED: в dds.dim_routes найдены NULL обязательные поля: %',
+            v_null_count;
+    END IF;
+
+    RAISE NOTICE
+        'DQ PASSED: dds.dim_routes ок, строк=% (версий)',
+        v_row_count;
+END $$;