feat: initial HSAP platform

Huaxu Sentinel Active Safety Platform with embedded algorithm code,
Docker Compose setup, and vendored dataset scaffolds for clone-and-run.

Co-authored-by: Cursor <cursoragent@cursor.com>

platform/as_platform/db/engine.py

@@ -0,0 +1,60 @@
+"""SQLAlchemy 引擎与会话。"""
+from __future__ import annotations
+
+from contextlib import contextmanager
+from typing import Generator
+
+from sqlalchemy import create_engine, event, text
+from sqlalchemy.orm import Session, declarative_base, sessionmaker
+
+from as_platform.config import DATABASE_URL, IS_POSTGRES, IS_SQLITE
+
+connect_args: dict = {}
+engine_kwargs: dict = {"future": True}
+
+if IS_SQLITE:
+    connect_args["check_same_thread"] = False
+elif IS_POSTGRES:
+    engine_kwargs.update(pool_pre_ping=True, pool_size=5, max_overflow=10)
+
+engine = create_engine(DATABASE_URL, connect_args=connect_args, **engine_kwargs)
+SessionLocal = sessionmaker(bind=engine, autocommit=False, autoflush=False, future=True)
+Base = declarative_base()
+
+
+@event.listens_for(engine, "connect")
+def _on_connect(dbapi_conn, _):
+    if IS_SQLITE:
+        cursor = dbapi_conn.cursor()
+        cursor.execute("PRAGMA foreign_keys=ON")
+        cursor.close()
+
+
+def check_connection() -> bool:
+    try:
+        with engine.connect() as conn:
+            conn.execute(text("SELECT 1"))
+        return True
+    except Exception:
+        return False
+
+
+@contextmanager
+def session_scope() -> Generator[Session, None, None]:
+    db = SessionLocal()
+    try:
+        yield db
+        db.commit()
+    except Exception:
+        db.rollback()
+        raise
+    finally:
+        db.close()
+
+
+def get_db() -> Generator[Session, None, None]:
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()