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

frontend/info.md

@@ -0,0 +1,31 @@
+Using Node.js 20, Tailwind CSS v3.4.19, and Vite v7.2.4
+
+Tailwind CSS has been set up with the shadcn theme
+
+Setup complete: /mnt/okcomputer/output/app
+
+Components (40+):
+  accordion, alert-dialog, alert, aspect-ratio, avatar, badge, breadcrumb,
+  button-group, button, calendar, card, carousel, chart, checkbox, collapsible,
+  command, context-menu, dialog, drawer, dropdown-menu, empty, field, form,
+  hover-card, input-group, input-otp, input, item, kbd, label, menubar,
+  navigation-menu, pagination, popover, progress, radio-group, resizable,
+  scroll-area, select, separator, sheet, sidebar, skeleton, slider, sonner,
+  spinner, switch, table, tabs, textarea, toggle-group, toggle, tooltip
+
+Usage:
+  import { Button } from '@/components/ui/button'
+  import { Card, CardHeader, CardTitle } from '@/components/ui/card'
+
+Structure:
+  src/sections/        Page sections
+  src/hooks/           Custom hooks
+  src/types/           Type definitions
+  src/App.css          Styles specific to the Webapp
+  src/App.tsx          Root React component
+  src/index.css        Global styles
+  src/main.tsx         Entry point for rendering the Webapp
+  index.html           Entry point for the Webapp
+  tailwind.config.js   Configures Tailwind's theme, plugins, etc.
+  vite.config.ts       Main build and dev server settings for Vite
+  postcss.config.js    Config file for CSS post-processing tools