fix(tradein-estimator): extend cohort filter to Tier S + Tier H, fix late_soviet overlap

PR #519 added cohort hard-filter but only to Tier W's inline SQL. Tier S
(address ILIKE) and Tier H (year ±15) share _COMMON_WHERE which was not
extended — for target_year=1978 (brezhnev), Tier H allowed year_built ∈
[1963, 1993] and a 1965 khrushchev or 1992 late_soviet match could win
before cohort filter ever evaluated.

Fixes (reviewer feedback on PR #519, item #1):
* Append cohort clause to _COMMON_WHERE so Tier S and Tier H inherit it.
* Add cohort_year_min/max binds to base_params (auto-propagates to both).
* Tier W's inline copy stays — not converted to _COMMON_WHERE (relevance_score
  CASE expressions require inline form). Comment near _COMMON_WHERE documents
  the dual code path requirement.

Also (reviewer item #5):
* Fix late_soviet range 1985-1999 → 1990-1999. Previous overlap with brezhnev
  1970-1989 + first-match semantics made late_soviet effectively cover only
  1990-1999 anyway — rename clarifies actual coverage.

Add parametrized pytest test_target_cohort_range covering None, out-of-range,
boundary cases, and the audit's target (1978 → brezhnev).

tradein-mvp/backend/app/services/estimator.py

@@ -71,7 +71,7 @@ COHORTS = (
     # (cohort_name, year_min_inclusive, year_max_inclusive)
     ('khrushchev',  1955, 1969),  # Хрущёвки 5-эт
     ('brezhnev',    1970, 1989),  # Брежневка кирпич/панель 9–12-эт
-    ('late_soviet', 1985, 1999),  # Поздний СССР (overlap с brezhnev intentional)
+    ('late_soviet', 1990, 1999),  # Поздний СССР (no overlap; first-match would never pick old range)
     ('2000s',       2000, 2010),  # Ранние новостройки
     ('modern',      2011, 2100),  # Современные ЖК
 )
@@ -1023,7 +1023,20 @@ _COMMON_WHERE = """
     AND is_active = true
     AND scraped_at > NOW() - (:fresh_days || ' days')::interval
     AND price_rub > 0
+    -- Когортный фильтр (PR 10): применяется к Tier S и Tier H через _COMMON_WHERE.
+    -- Tier W имеет свою копию этого блока в inline SQL. Если cohort_year_min IS NULL —
+    -- фильтр прозрачен. CAST обязателен — psycopg3 prepared statement не выводит
+    -- тип $N при IS NULL в predicate (см. PR #518 fix).
+    AND (
+        CAST(:cohort_year_min AS integer) IS NULL
+        OR year_built IS NULL
+        OR year_built BETWEEN CAST(:cohort_year_min AS integer)
+                          AND CAST(:cohort_year_max AS integer)
+    )
 """
+# Note: Tier W has its own inline copy of the cohort clause (PR #519 line
+# ~1280). Не удалять — Tier W не использует _COMMON_WHERE из-за inline
+# relevance_score CASE expressions. Both code paths must stay in sync.
 
 
 def _fetch_analogs(
@@ -1073,6 +1086,8 @@ def _fetch_analogs(
         "area_max": area_max,
         "fresh_days": LISTINGS_FRESH_DAYS,
         "max_per_addr": MAX_ANALOGS_PER_ADDRESS,
+        "cohort_year_min": cohort_year_min,
+        "cohort_year_max": cohort_year_max,
     }
 
     # ── Tier S: same building ─────────────────────────────────────────────────

tradein-mvp/backend/tests/test_estimator_cohort.py

@@ -0,0 +1,43 @@
+"""Unit tests for cohort filter helpers in estimator.py.
+
+PR 10 (2026-05-24) — covers _target_cohort_range edge cases:
+None, out-of-range, exact boundaries, first-match semantics.
+"""
+import os
+
+# Settings requires DATABASE_URL at init time. Set dummy DSN before any app import.
+os.environ.setdefault("DATABASE_URL", "postgresql://test:test@localhost/test_db")
+
+import pytest
+
+from app.services.estimator import _target_cohort_range
+
+
+@pytest.mark.parametrize(
+    ("year", "expected"),
+    [
+        (None,        None),               # no year → no cohort
+        (1900,        None),               # out-of-range below → no cohort
+        (1954,        None),               # below khrushchev floor
+        (1955,        (1955, 1969)),       # khrushchev floor
+        (1960,        (1955, 1969)),       # khrushchev mid
+        (1969,        (1955, 1969)),       # khrushchev ceiling
+        (1970,        (1970, 1989)),       # brezhnev floor
+        (1978,        (1970, 1989)),       # brezhnev (target audit case)
+        (1988,        (1970, 1989)),       # brezhnev pre-overlap fix held
+        (1989,        (1970, 1989)),       # brezhnev ceiling
+        (1990,        (1990, 1999)),       # late_soviet floor (post-PR10 fix)
+        (1995,        (1990, 1999)),       # late_soviet mid
+        (1999,        (1990, 1999)),       # late_soviet ceiling
+        (2000,        (2000, 2010)),       # 2000s floor
+        (2010,        (2000, 2010)),       # 2000s ceiling
+        (2011,        (2011, 2100)),       # modern floor
+        (2024,        (2011, 2100)),       # modern current
+        (2100,        (2011, 2100)),       # modern ceiling
+        (2101,        None),               # above modern ceiling → no cohort
+        (2200,        None),               # far future → no cohort
+    ],
+)
+def test_target_cohort_range(year, expected):
+    """First-match cohort mapping; out-of-range and None → None."""
+    assert _target_cohort_range(year) == expected