refactor: 标准化项目结构 frontend/ + backend/ + SQLite + run.sh

- 目录重构: app/ -> frontend/，与 backend/ 并列
- 数据库: 默认 SQLite（零配置），修复 DSN() bug
- run.sh: 一键启动前后端，支持 start/stop/restart/status
- Makefile: install/dev/build/lint/clean 快捷命令
- vite.config.ts: 配置 dev server 端口 5173 + API 代理到 8080
- config.yaml: SQLite 默认配置，开箱即用
- docs/: 完整开发文档（项目结构/API/数据库/规范/部署）
- 修复: GORM foreign key 关联声明
- 修复: go get gorm.io/driver/sqlite 依赖

Makefile

@@ -0,0 +1,62 @@
+# EZOps AIOps - Makefile
+.PHONY: help install dev build clean status stop restart lint
+
+help:
+	@echo "EZOps AIOps - 可用命令:"
+	@echo ""
+	@echo "  make install    - 安装前后端依赖"
+	@echo "  make dev        - 启动开发环境（前后端）"
+	@echo "  make build      - 构建生产环境（前后端）"
+	@echo "  make build-ui   - 仅构建前端"
+	@echo "  make build-api  - 仅构建后端"
+	@echo "  make status     - 查看服务状态"
+	@echo "  make stop       - 停止所有服务"
+	@echo "  make restart    - 重启所有服务"
+	@echo "  make logs       - 查看实时日志"
+	@echo "  make lint       - 代码检查"
+	@echo "  make clean      - 清理构建产物"
+	@echo ""
+
+install:
+	@echo "安装后端依赖..."
+	cd backend && go mod download
+	@echo "安装前端依赖..."
+	cd frontend && npm install
+
+dev:
+	./run.sh start
+
+build-ui:
+	@echo "构建前端..."
+	cd frontend && npm run build
+
+build-api:
+	@echo "构建后端..."
+	cd backend && CGO_ENABLED=1 go build -o aiops-server cmd/main.go
+
+build: build-api build-ui
+
+status:
+	./run.sh status
+
+stop:
+	./run.sh stop
+
+restart:
+	./run.sh restart
+
+logs:
+	@tail -f backend/logs/server.log frontend/logs/dev.log 2>/dev/null || echo "日志文件不存在"
+
+lint:
+	@echo "检查后端代码..."
+	cd backend && go vet ./...
+	@echo "检查前端代码..."
+	cd frontend && npm run lint 2>/dev/null || echo "前端 lint 未配置，跳过"
+
+clean:
+	@echo "清理构建产物..."
+	rm -f backend/aiops-server
+	rm -rf frontend/dist
+	rm -f backend/logs/*.log frontend/logs/*.log
+	@echo "清理完成"