feat(runtime): dcy-014 trading_date KST 타임존 분리 + 일일 슬롯 preallocation (BAT-018)

데몬이 시스템 UTC 날짜로 슬롯을 1회만 preallocate 해 trading_date 가 KST 캘린더와
어긋나고 재시작 없이는 다음날 슬롯이 안 생기던 문제(issue #14) 정정.

거버넌스: 전부 change-req (신규 REQ 없음, dcy-014 OQ-3; 스케줄러는 REQ-030 패턴 준용).
- REQ-005: trading_date 를 설정 타임존(기본 Asia/Seoul) 기준 계산(timestamp 는 UTC
  유지). DailyPreallocationScheduler 신규 — TZ 일자당 1회 멱등 fire, 재시작 없이
  다음날 슬롯 자동 생성. setup() 배선 + trex-preallocation 스레드
- REQ-048: TOML trading_timezone/daily_preallocation_time 키 + from_config 전파
- REQ-009: runtime-flows/data-model 정합 + instance.example.toml

OQ-1 기본 00:00(TZ 자정, TOML 설정 가능) / OQ-2 매 캘린더일 생성(거래일 캘린더 후속).
멱등 preallocate 로 중복 tick·다중 인스턴스 중복 생성 0.

검증: 단위 302 passed/32 skipped, 인프라 게이트(PG+RabbitMQ) 334 passed, ruff clean.
신규 test_preallocation_scheduler(고정 clock) + test_instance_config 확장.
BAT-018 release-candidate.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

trex_core/application/preallocation_scheduler.py

@@ -0,0 +1,72 @@
+"""Daily slot preallocation scheduler (dcy-014 / REQ-005, issue #14).
+
+trading_date is computed in a configurable timezone (default Asia/Seoul) so the
+DB trading_date matches the local trading calendar, while all timestamps stay
+UTC (NFR-1). Modeled on SnapshotScheduler (REQ-030): a tick loop fires once per
+TZ-day at/after the configured trigger time, calling the idempotent
+`preallocate_daily_slots` so the next day's slots are created without a daemon
+restart (NFR-2/NFR-3).
+"""
+from __future__ import annotations
+
+import logging
+import threading
+from datetime import date, datetime, time, timezone
+from typing import Callable, Optional, Protocol
+
+_log = logging.getLogger(__name__)
+
+
+class _Preallocator(Protocol):
+    def preallocate_daily_slots(self, trading_date: date, count: int) -> int:
+        ...
+
+
+class DailyPreallocationScheduler:
+    """Background-thread-friendly daily preallocation. Use `run_once()` for tests."""
+
+    def __init__(
+        self,
+        *,
+        slot_service: _Preallocator,
+        total_slots: int,
+        tz: timezone,
+        schedule_time: time = time(hour=0, minute=0),
+        clock: Optional[Callable[[], datetime]] = None,
+    ) -> None:
+        self._svc = slot_service
+        self._total = total_slots
+        self._tz = tz  # tzinfo used to derive trading_date (default Asia/Seoul)
+        self._schedule = schedule_time
+        self._clock = clock or (lambda: datetime.now(tz=timezone.utc))
+        self._last_fired_date: Optional[date] = None
+
+    # ---- callable from a daemon thread loop --------------------------------
+    def run_forever(self, stop: threading.Event, *, tick_sec: float = 60.0) -> None:
+        # Boot: ensure the current TZ-day's slots exist immediately (idempotent),
+        # then enter the daily cadence for subsequent day boundaries.
+        self.run_once()
+        while not stop.wait(tick_sec):
+            try:
+                self._maybe_tick()
+            except Exception:  # noqa: BLE001 - loop must survive transient errors
+                _log.exception("preallocation scheduler tick failed")
+
+    def _maybe_tick(self) -> None:
+        now_tz = self._clock().astimezone(self._tz)
+        target = datetime.combine(now_tz.date(), self._schedule, tzinfo=self._tz)
+        if now_tz < target:
+            return  # before today's trigger time
+        if self._last_fired_date is not None and self._last_fired_date == now_tz.date():
+            return  # already created today's slots
+        self.run_once()
+
+    # ---- the actual preallocation -----------------------------------------
+    def run_once(self) -> date:
+        """Preallocate slots for the current TZ trading_date (idempotent). Returns it."""
+        trading_date = self._clock().astimezone(self._tz).date()
+        created = self._svc.preallocate_daily_slots(trading_date, self._total)
+        if created:
+            _log.info("preallocated %d slots for trading_date=%s", created, trading_date)
+        self._last_fired_date = trading_date
+        return trading_date