fix(security): require authentication for image file endpoint (H-2)

- Changed /api/v1/files/image from AuthType.NONE to USER_TOKEN_OR_API_KEY
- Added Permission.RESOURCE_VIEW requirement
- Prevents unauthenticated cross-tenant file access via leaked keys
- Fixes HIGH severity finding from multi-tenant security review

docs: add comprehensive database migration guide
- Complete migration steps for OSS → multi-tenant
- Backup, execution, verification procedures
- Rollback scenarios and recovery plans
- Performance tuning recommendations

docs/multi-tenant/DATABASE_MIGRATION_GUIDE.md

@@ -0,0 +1,166 @@
+# LangBot 多租户数据库迁移指南
+
+## 概述
+
+LangBot 从单租户 OSS 架构迁移到多租户 SaaS 架构，需要执行 7 个数据库迁移（0009-0015）。
+
+## 迁移序列
+
+```
+0009_workspace_tenancy_kernel → 创建 Workspace、成员、邀请表
+0010_scope_tenant_resources → 所有业务表添加 workspace_uuid
+0011_postgres_tenant_rls → PostgreSQL 行级安全策略
+0012_plugin_installation_identity → 插件实例租户绑定
+0013_tenant_pgvector → RAG 向量存储隔离
+0014_cloud_directory_projection → Cloud 控制平面同步
+0015_cloud_core_collaboration → 协作和权限功能
+```
+
+## 执行步骤
+
+### 1. 备份（必须）
+
+```bash
+# SQLite
+cp ~/.langbot/data/langbot.db ~/.langbot/data/langbot.db.backup-$(date +%Y%m%d)
+
+# PostgreSQL  
+pg_dump -U langbot_user -d langbot_db -F c -f langbot_backup_$(date +%Y%m%d).dump
+```
+
+### 2. 执行迁移
+
+```bash
+# 停止服务
+sudo -S -p '' systemctl stop langbot
+
+# 执行迁移
+python -m langbot.pkg.persistence.migration upgrade head
+
+# 验证
+python -m langbot.pkg.persistence.migration current
+# 预期: 0015_cloud_core_collaboration
+
+# 启动服务
+sudo -S -p '' systemctl start langbot
+```
+
+### 3. OSS 单租户自动迁移
+
+迁移会自动：
+- 创建默认 Workspace（名称："Default Workspace"）
+- 第一个用户成为 Owner
+- 所有现有资源绑定到该 Workspace
+
+### 4. 验证检查
+
+```bash
+# 检查 Workspace
+python << EOF
+from langbot.pkg.persistence import manager
+import sqlalchemy as sa
+
+with manager.engine.connect() as conn:
+    ws = conn.execute(sa.text("SELECT uuid, name FROM workspaces LIMIT 1")).first()
+    print(f"Workspace: {ws[1]} ({ws[0]})")
+    
+    # 检查资源绑定
+    bot_count = conn.execute(sa.text(
+        f"SELECT COUNT(*) FROM bots WHERE workspace_uuid='{ws[0]}'"
+    )).scalar()
+    print(f"Bots: {bot_count}")
+EOF
+```
+
+## 回滚方案
+
+### 完全回滚（丢失多租户数据）
+
+```bash
+# 1. 停止服务
+sudo -S -p '' systemctl stop langbot
+
+# 2. 恢复备份
+cp ~/.langbot/data/langbot.db.backup-YYYYMMDD ~/.langbot/data/langbot.db
+
+# 3. 回退代码
+git checkout v4.10.x
+pip install -e .
+
+# 4. 启动
+sudo -S -p '' systemctl start langbot
+```
+
+### 降级迁移（保留数据但移除多租户）
+
+```bash
+# 警告：会移除 Workspace 表但保留资源
+python -m langbot.pkg.persistence.migration downgrade 0008_mcp_resource_prefs
+```
+
+## 常见问题
+
+### Q: 迁移后无法登录
+
+```bash
+# 检查用户 UUID
+python << EOF
+from langbot.pkg.persistence import manager
+import sqlalchemy as sa
+
+with manager.engine.connect() as conn:
+    users = conn.execute(sa.text("SELECT id, user, uuid, status FROM users")).all()
+    for u in users:
+        print(f"{u[1]}: UUID={u[2]}, Status={u[3]}")
+EOF
+```
+
+### Q: 资源看不见了
+
+检查 Workspace 上下文：
+```bash
+# 前端请求需要带 X-Workspace-ID header
+curl -H "Authorization: Bearer $TOKEN" \
+     -H "X-Workspace-ID: $WORKSPACE_UUID" \
+     http://localhost:5200/api/v1/platform/bots
+```
+
+### Q: 迁移速度慢
+
+```bash
+# SQLite 优化
+sqlite3 ~/.langbot/data/langbot.db << EOF
+PRAGMA journal_mode=WAL;
+PRAGMA synchronous=NORMAL;
+VACUUM;
+EOF
+```
+
+## 性能调优
+
+### PostgreSQL 索引
+
+```sql
+-- 迁移后创建
+CREATE INDEX CONCURRENTLY idx_model_providers_workspace 
+    ON model_providers(workspace_uuid);
+
+CREATE INDEX CONCURRENTLY idx_bots_workspace 
+    ON bots(workspace_uuid);
+
+CREATE INDEX CONCURRENTLY idx_pipelines_workspace 
+    ON pipelines(workspace_uuid);
+```
+
+## 预估时间
+
+- SQLite < 100MB: 2-5 分钟
+- SQLite 100MB-1GB: 5-15 分钟  
+- PostgreSQL: < 5 分钟（取决于数据量）
+
+## 支持
+
+问题反馈：https://github.com/langbot-app/LangBot/issues
+
+**版本**: 1.0  
+**最后更新**: 2026-07-30