fix(leads): replace ::interval cast with make_interval (psycopg v3 trap) (#1383 follow-up)

(:bind || ' months')::interval is a psycopg v3 SyntaxError — the driver
sees '::' immediately after the bind placeholder token and chokes.
Replace all 6 occurrences (admin_leads.py + analytics_queries.py) with
make_interval(months => :bind) which is unambiguous to the parser and
semantically identical.

backend/app/api/v1/admin_leads.py

@@ -138,7 +138,7 @@ def leads_stats(
             WITH window_leads AS (
                 SELECT *
                   FROM prinzip_leads
-                 WHERE created_at >= NOW() - (:m || ' months')::interval
+                 WHERE created_at >= NOW() - make_interval(months => :m)
             )
             SELECT
                 (SELECT COUNT(*) FROM prinzip_leads) AS leads_total,

backend/app/services/analytics_queries.py

@@ -184,8 +184,7 @@ def quartirography(db: Session, source: str, region_id: int = 66) -> list[dict[s
                    -- ('2025-07-01' расширял «recent»-окно каждую неделю по мере
                    -- доливки ETL новых report_months → перекос в сторону всё
                    -- более длинной истории). Тот же фикс, что #1203 и _BUCKET_SQL.
-                   AND period_start_date >= NOW()
-                                          - (:months_window || ' months')::INTERVAL
+                   AND period_start_date >= NOW() - make_interval(months => :months_window)
             ),
             bucketed AS (
                 SELECT CASE
@@ -1169,7 +1168,7 @@ def prinzip_funnel_monthly(db: Session, months: int = 24) -> list[dict[str, Any]
                 """
             SELECT month, source, leads, engaged, converted, conv_pct
               FROM prinzip_funnel_monthly
-             WHERE month >= (CURRENT_DATE - (:months || ' months')::interval)::date
+             WHERE month >= (CURRENT_DATE - make_interval(months => :months))::date
              ORDER BY month DESC, leads DESC
             """
             ),
@@ -1203,7 +1202,7 @@ def prinzip_funnel_by_source(db: Session, months: int = 12) -> list[dict[str, An
                    SUM(converted) AS converted,
                    ROUND(100.0 * SUM(converted) / NULLIF(SUM(leads), 0), 2) AS conv_pct
               FROM prinzip_funnel_monthly
-             WHERE month >= (CURRENT_DATE - (:months || ' months')::interval)::date
+             WHERE month >= (CURRENT_DATE - make_interval(months => :months))::date
              GROUP BY source
              ORDER BY leads DESC
             """
@@ -1364,8 +1363,7 @@ _BUCKET_SQL = text(
            AND deal_count > 0
            AND (area / deal_count) BETWEEN 15 AND 200
            AND price_per_sqm BETWEEN 30000 AND 1000000
-           AND period_start_date >= NOW()
-                                  - (:months_window || ' months')::INTERVAL
+           AND period_start_date >= NOW() - make_interval(months => :months_window)
     ),
     bucketed AS (
         SELECT CASE
@@ -1995,7 +1993,7 @@ def _elasticity_coef(
                        {where_district}
                        {where_class}
                        AND crm.deals_total_avg_price_thousand_rub_per_m2 > 0
-                       AND crm.report_month >= NOW() - (:ew || ' months')::interval
+                       AND crm.report_month >= NOW() - make_interval(months => :ew)
                 )
                 SELECT
                     regr_slope(y, x) AS slope,
@@ -2086,7 +2084,7 @@ def _elasticity_per_bucket_coef(
                        {where_class}
                        AND crm.deals_total_count > 0
                        AND crm.deals_total_avg_price_thousand_rub_per_m2 > 0
-                       AND crm.report_month >= NOW() - (:ew || ' months')::interval
+                       AND crm.report_month >= NOW() - make_interval(months => :ew)
                 )
                 SELECT bucket,
                        regr_slope(y, x)  AS slope,