feat: 添加平台管理、计算模块适配器及前端页面更新

- 新增 platform API 端点和存储
- 新增 llama_factory 适配器
- 新增前端 compute、guide、system 等视图页面
- 新增 echarts 插件和 mock 数据
- 更新 Docker 配置、后端配置及文档
- 更新前端路由、API、侧边栏等组件

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

backend/app/db/session.py

@@ -1,4 +1,41 @@
-"""Database session factory placeholder.
+from __future__ import annotations
+
+import os
+from collections.abc import Generator
+from contextlib import contextmanager
+
+from sqlalchemy import create_engine
+from sqlalchemy.orm import Session, sessionmaker
+
+
+DATABASE_URL = os.getenv("DATABASE_URL", "sqlite:///./runtime/platform.db")
+
+engine = create_engine(
+    DATABASE_URL,
+    pool_pre_ping=True,
+    future=True,
+    connect_args={"check_same_thread": False} if DATABASE_URL.startswith("sqlite") else {},
+)
+SessionLocal = sessionmaker(bind=engine, autoflush=False, autocommit=False, expire_on_commit=False, future=True)
+
+
+def get_db() -> Generator[Session, None, None]:
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
+
+
+@contextmanager
+def session_scope() -> Generator[Session, None, None]:
+    db = SessionLocal()
+    try:
+        yield db
+        db.commit()
+    except Exception:
+        db.rollback()
+        raise
+    finally:
+        db.close()
 
-Implement SQLAlchemy/SQLModel session management here when database development starts.
-"""