ems-core v1.0.0: Standard EMS platform core

Shared backend + frontend for multi-customer EMS deployments.
- 12 enterprise modules: quota, cost, charging, maintenance, analysis, etc.
- 120+ API endpoints, 37 database tables
- Customer config mechanism (CUSTOMER env var + YAML config)
- Collectors: Modbus TCP, MQTT, HTTP API, Sungrow iSolarCloud
- Frontend: React 19 + Ant Design + ECharts + Three.js
- Infrastructure: Redis cache, rate limiting, aggregation engine

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/core/database.py

@@ -0,0 +1,27 @@
+from sqlalchemy.ext.asyncio import create_async_engine, async_sessionmaker, AsyncSession
+from sqlalchemy.orm import DeclarativeBase
+from app.core.config import get_settings
+
+settings = get_settings()
+
+engine_kwargs = {"echo": settings.DEBUG}
+if not settings.is_sqlite:
+    engine_kwargs["pool_size"] = 20
+    engine_kwargs["max_overflow"] = 10
+
+engine = create_async_engine(settings.DATABASE_URL, **engine_kwargs)
+async_session = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+async def get_db():
+    async with async_session() as session:
+        try:
+            yield session
+            await session.commit()
+        except Exception:
+            await session.rollback()
+            raise