feat: postgres history-first 계약과 적재 경로 추가

- PostgreSQL history contract와 schema/validator를 추가했습니다.
- .NET history store, snapshot reader, repository, migration을 연결했습니다.
- history-first 운영 모델 문서와 daily signal tracking 문구를 정리했습니다.

src/quant_engine/postgresql_history_store_v1.py

@@ -0,0 +1,82 @@
+"""PostgreSQL history store for engine provenance tracking.
+
+This module is intentionally thin: it owns connection, table routing, append
+operations, and snapshot reads for the history-first operating model.
+"""
+from __future__ import annotations
+
+import json
+from dataclasses import dataclass
+from pathlib import Path
+from typing import Any, Iterable
+
+
+DOMAIN_TABLES = {
+    "market_raw_history": "engine_history.market_raw_history",
+    "factor_version_history": "engine_history.factor_version_history",
+    "factor_output_history": "engine_history.factor_output_history",
+    "decision_result_history": "engine_history.decision_result_history",
+    "market_vs_engine_gap_history": "engine_history.market_vs_engine_gap_history",
+}
+
+
+@dataclass(frozen=True)
+class HistoryRow:
+    domain: str
+    payload: dict[str, Any]
+
+
+def _is_pg_dsn(value: str) -> bool:
+    return value.startswith("postgresql://") or value.startswith("postgres://")
+
+
+def connect(dsn_or_path: str | Path) -> Any:
+    value = str(dsn_or_path)
+    if _is_pg_dsn(value):
+        try:
+            import psycopg2
+        except ImportError as exc:
+            raise ImportError("PostgreSQL DSN requires psycopg2") from exc
+        return psycopg2.connect(value)
+    raise ValueError("postgresql_history_store_v1 only accepts a PostgreSQL DSN")
+
+
+def ensure_schema(conn: Any) -> None:
+    sql = """
+    CREATE SCHEMA IF NOT EXISTS engine_history;
+    """
+    cur = conn.cursor()
+    cur.execute(sql)
+    conn.commit()
+
+
+def append_row(conn: Any, domain: str, payload: dict[str, Any]) -> None:
+    table = DOMAIN_TABLES.get(domain)
+    if not table:
+        raise KeyError(f"unknown domain: {domain}")
+    ensure_schema(conn)
+    keys = [k for k in payload.keys() if k != "id"]
+    cols = ", ".join(keys + ["provenance"])
+    placeholders = ", ".join(["%s"] * (len(keys) + 1))
+    values = [json.dumps(payload.get(k), ensure_ascii=False, default=str) if isinstance(payload.get(k), (dict, list)) else payload.get(k) for k in keys]
+    values.append(json.dumps(payload.get("provenance") or {}, ensure_ascii=False, default=str))
+    sql = f"INSERT INTO {table} ({cols}) VALUES ({placeholders})"
+    cur = conn.cursor()
+    cur.execute(sql, values)
+    conn.commit()
+
+
+def append_rows(conn: Any, rows: Iterable[HistoryRow]) -> None:
+    for row in rows:
+        append_row(conn, row.domain, row.payload)
+
+
+def snapshot_table(conn: Any, domain: str, limit: int = 1000) -> list[dict[str, Any]]:
+    table = DOMAIN_TABLES.get(domain)
+    if not table:
+        raise KeyError(f"unknown domain: {domain}")
+    cur = conn.cursor()
+    cur.execute(f"SELECT * FROM {table} ORDER BY created_at DESC LIMIT %s", (limit,))
+    columns = [col[0] for col in cur.description]
+    return [dict(zip(columns, row)) for row in cur.fetchall()]
+