fix(tradein): renumber obj_class migration to 121 + drop no-op DISTINCT ON (#572)

- git mv 120_backfill_obj_class_kn_api.sql → 121 (120 taken by kn_price_per_m2 on main)
- Update header comment and RAISE NOTICE message to reference 121
- Pass 2 subquery: remove DISTINCT ON (obj_id, snapshot_date) — CROSS JOIN LATERAL
  with LIMIT 1 already guarantees one row per pair; DISTINCT ON was misleading
- domrf_kn.py: add one-line note that r"типов" pattern is intentionally broad given
  DOM.RF aiDescription inflection variety (tightening risks <70% coverage)

backend/app/services/scrapers/domrf_kn.py

@@ -143,6 +143,8 @@ _OBJ_CLASS_PATTERNS: list[tuple[str, str]] = [
     # that use the word "типов*" to describe standard/economy housing. The canonical value
     # "Типовой" matches what the catalog SSR scraper (domrf_catalog.py) extracts from pages.
     # Bug #572: this pattern was absent → 131+ objects remained NULL despite matching aiDescription.
+    # Intentionally broad (r"типов" not r"типов[ыоа]й?\b"): DOM.RF aiDescription uses varied
+    # inflections; tightening risks dropping coverage below the 70% acceptance threshold.
     (r"типов", "Типовой"),
 ]
 

data/sql/121_backfill_obj_class_kn_api.sql

@@ -1,4 +1,4 @@
--- 120_backfill_obj_class_kn_api.sql
+-- 121_backfill_obj_class_kn_api.sql
 --
 -- Backfill obj_class for domrf_kn_objects rows that remain NULL after migration 106.
 --
@@ -75,7 +75,7 @@ WHERE o.obj_id    = src.obj_id
 UPDATE domrf_kn_objects AS o
 SET obj_class = prev.obj_class
 FROM (
-    SELECT DISTINCT ON (n.obj_id, n.snapshot_date)
+    SELECT
         n.obj_id,
         n.snapshot_date,
         best.obj_class
@@ -145,7 +145,7 @@ BEGIN
      WHERE snapshot_date = v_latest_snap AND region_cd = 66;
 
     RAISE NOTICE
-        'domrf_kn_objects after 120 backfill:'
+        'domrf_kn_objects after 121 backfill:'
         ' all-snapshots: total=% filled=% null=%'
         ' | latest snapshot (%): total=% filled=%',
         v_total, v_filled, v_null,