Initial commit: stock analysis backend and prototype UI.

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

backend/db.py

@@ -0,0 +1,43 @@
+"""数据库引擎与初始化。
+
+init_db():
+- 若目标库不存在则自动创建（连到默认 postgres 库执行 CREATE DATABASE）
+- 建表
+"""
+from __future__ import annotations
+
+import psycopg2
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+
+import config
+from models import Base
+
+engine = create_engine(config.DB_URL, pool_pre_ping=True, future=True)
+SessionLocal = sessionmaker(bind=engine, autoflush=False, expire_on_commit=False, future=True)
+
+
+def _ensure_database():
+    try:
+        conn = psycopg2.connect(
+            host=config.PG_HOST, port=config.PG_PORT, user=config.PG_USER,
+            password=config.PG_PASSWORD, dbname="postgres", connect_timeout=5)
+        conn.autocommit = True
+        cur = conn.cursor()
+        cur.execute("SELECT 1 FROM pg_database WHERE datname = %s", (config.PG_DB,))
+        if not cur.fetchone():
+            cur.execute(f'CREATE DATABASE "{config.PG_DB}"')
+        cur.close()
+        conn.close()
+    except Exception as e:  # 数据库已存在或无权限时不阻断
+        print("[db] ensure_database:", repr(e)[:120])
+
+
+def init_db():
+    _ensure_database()
+    Base.metadata.create_all(engine)
+    print("[db] tables ready")
+
+
+def get_session():
+    return SessionLocal()