fix(tradein): migration 100 — enable deactivate_stale_avito schedule on prod (#759)

Root cause: migration 090 used ON CONFLICT (source) DO NOTHING; prod already had
a row source='deactivate_stale_avito' with enabled=false (inserted before 090 ran),
so the INSERT was silently skipped. The scheduler's WHERE enabled=true filter meant
the task never fired (last_run_id=NULL, next_run_at=2026-06-01 expired).

Fix: add migration 100 — idempotent UPDATE SET enabled=true, next_run_at=NOW()
WHERE source='deactivate_stale_avito' AND enabled=false. Safe to re-run: 0 rows
matched once the row is already enabled. Auto-applied on next deploy via
_schema_migrations tracking in deploy-tradein.yml.

Migration 090 seed (enabled=true + ON CONFLICT DO NOTHING) is already correct for
fresh installs — no change needed there.

Tests: 7 new assertions in test_deactivate_stale_avito.py for migration 100
(exists, UPDATE source, SET enabled=true, idempotent guard, BEGIN/COMMIT, no
psycopg trap, next_run_at reset). 39 tests pass total.

Refs #759

tradein-mvp/backend/data/sql/100_enable_deactivate_stale_avito.sql

@@ -0,0 +1,19 @@
+-- #759: deactivate_stale_avito schedule seeded enabled=false → task never ran on prod.
+--
+-- Root cause: migration 090 (ON CONFLICT (source) DO NOTHING) was a no-op because
+-- the row 'deactivate_stale_avito' already existed in scrape_schedules with
+-- enabled=false when 090 ran on prod (inserted by a pre-release iteration or manual
+-- seed). The scheduler's WHERE enabled=true filter excluded it on every tick, so
+-- last_run_id stayed NULL and next_run_at=2026-06-01 expired without any runs.
+--
+-- Fix: idempotent UPDATE that only fires when the row is still disabled.
+-- Re-running this migration after the row is already enabled → 0 rows matched, safe.
+--
+-- No bind params → no CAST(:x AS type) needed; BEGIN/COMMIT per sql.md conventions.
+BEGIN;
+UPDATE scrape_schedules
+   SET enabled    = true,
+       next_run_at = NOW()
+ WHERE source  = 'deactivate_stale_avito'
+   AND enabled = false;
+COMMIT;

tradein-mvp/backend/tests/test_deactivate_stale_avito.py

@@ -252,3 +252,53 @@ def test_failure_path_rollback_and_mark_failed(monkeypatch: pytest.MonkeyPatch)
 
     assert db.rolled_back is True
     assert failed["run_id"] == 7
+
+
+# ── Migration 100: prod hot-fix — flip enabled=false → true ──────────────────
+
+_MIGRATION_100 = _SQL_DIR / "100_enable_deactivate_stale_avito.sql"
+
+
+def test_migration_100_exists() -> None:
+    """Prod hot-fix migration must be present so deploy auto-applies it."""
+    assert _MIGRATION_100.is_file(), f"missing migration: {_MIGRATION_100}"
+
+
+def test_migration_100_updates_correct_source() -> None:
+    sql = _MIGRATION_100.read_text("utf-8")
+    assert "'deactivate_stale_avito'" in sql
+
+
+def test_migration_100_sets_enabled_true() -> None:
+    sql = _MIGRATION_100.read_text("utf-8")
+    # UPDATE … SET enabled = true
+    assert re.search(
+        r"enabled\s*=\s*true", sql, re.IGNORECASE
+    ), "migration 100 must SET enabled = true"
+
+
+def test_migration_100_is_idempotent() -> None:
+    """WHERE enabled = false ensures re-running after fix → 0 rows matched."""
+    sql = _MIGRATION_100.read_text("utf-8")
+    assert re.search(
+        r"enabled\s*=\s*false", sql, re.IGNORECASE
+    ), "migration 100 must guard with AND enabled = false for idempotency"
+
+
+def test_migration_100_is_transactional() -> None:
+    sql = _MIGRATION_100.read_text("utf-8")
+    assert "BEGIN;" in sql
+    assert "COMMIT;" in sql
+
+
+def test_migration_100_no_psycopg_trap() -> None:
+    """Plain DML — no bind params — guard :x::type trap anyway."""
+    sql = _MIGRATION_100.read_text("utf-8")
+    assert not re.search(r":\w+::", sql)
+
+
+def test_migration_100_also_resets_next_run_at() -> None:
+    """next_run_at = NOW() ensures the scheduler fires on the next tick."""
+    sql = _MIGRATION_100.read_text("utf-8")
+    assert "next_run_at" in sql
+    assert "NOW()" in sql