feat(m0): 后端骨架 + Web/安卓前端骨架 + 设计文档

- backend: FastAPI 应用工厂、统一错误信封、JWT、短信登录、工作区/成员/邀请、幂等中间件
- alembic 0001: workspace/member/invitation/audit_log/app_user + RLS 策略 + 双角色 GRANT
- tests: 认证/工作区/租户隔离/幂等 四组用例（尚未在本机执行）
- web: React18+Vite 骨架（登录、工作区、邀请落地页）
- android: Compose 骨架（登录、工作区列表）
- 2.Design: PRODUCT-PLAN / ROADMAP-M0-M1 / NAMING / DEVELOPMENT

web/src/index.css

@@ -0,0 +1,37 @@
+@tailwind base;
+@tailwind components;
+@tailwind utilities;
+
+@layer base {
+  html,
+  body,
+  #root {
+    height: 100%;
+  }
+  body {
+    @apply bg-ink-50 text-ink-900 antialiased;
+  }
+}
+
+@layer components {
+  .card {
+    @apply rounded-xl border border-ink-100 bg-white p-5 shadow-sm;
+  }
+  .btn {
+    @apply inline-flex items-center justify-center rounded-lg px-4 py-2 text-sm font-medium
+      transition disabled:cursor-not-allowed disabled:opacity-50;
+  }
+  .btn-primary {
+    @apply btn bg-ink-700 text-white hover:bg-ink-900;
+  }
+  .btn-ghost {
+    @apply btn border border-ink-100 bg-white text-ink-700 hover:bg-ink-50;
+  }
+  .input {
+    @apply w-full rounded-lg border border-ink-100 bg-white px-3 py-2 text-sm
+      outline-none focus:border-ink-500 focus:ring-2 focus:ring-ink-500/20;
+  }
+  .label {
+    @apply mb-1 block text-xs font-medium text-ink-500;
+  }
+}