feat(web): 升级前端依赖并重构邮件编辑器

- 将前端包管理切换为 `pnpm`，新增工作区与锁文件，并同步更新 CI 与 Docker 构建流程。
- 引入 `tiptap` 重构邮件正文编辑器，支持预览、富文本样式、链接/图片编辑与日程卡片插入。
- 发送与定时发送新增确认提示，补充空主题、空正文和附件提醒。
- 更新 `README.md` 与 `SHADCN_RULES.md` 中的安装与检查命令。

deploy/all-in-one/Dockerfile

@@ -11,12 +11,14 @@ RUN --mount=type=cache,target=/go/pkg/mod \
     CGO_ENABLED=0 GOOS=linux go build -trimpath -o /out/lanqin-api ./cmd/server
 
 FROM node:20-bookworm-slim AS web-build
-WORKDIR /src/apps/web
-COPY apps/web/package.json apps/web/package-lock.json* ./
-RUN --mount=type=cache,target=/root/.npm \
-    npm ci --prefer-offline --no-audit || npm install --prefer-offline --no-audit
-COPY apps/web ./
-RUN npm run build
+WORKDIR /src
+COPY pnpm-lock.yaml pnpm-workspace.yaml ./
+COPY apps/web/package.json apps/web/package.json
+RUN corepack enable && corepack prepare pnpm@10.28.2 --activate
+RUN --mount=type=cache,target=/root/.local/share/pnpm/store \
+    pnpm install --frozen-lockfile --filter lanqin-email-web...
+COPY apps/web apps/web
+RUN pnpm --dir apps/web run build
 
 FROM debian:bookworm-slim
 ENV DEBIAN_FRONTEND=noninteractive

deploy/web.Dockerfile

@@ -1,12 +1,14 @@
 # syntax=docker/dockerfile:1.7
 
 FROM node:20-bookworm-slim AS build
-WORKDIR /src/apps/web
-COPY apps/web/package.json apps/web/package-lock.json* ./
-RUN --mount=type=cache,target=/root/.npm \
-    npm ci --prefer-offline --no-audit || npm install --prefer-offline --no-audit
-COPY apps/web ./
-RUN npm run build
+WORKDIR /src
+COPY pnpm-lock.yaml pnpm-workspace.yaml ./
+COPY apps/web/package.json apps/web/package.json
+RUN corepack enable && corepack prepare pnpm@10.28.2 --activate
+RUN --mount=type=cache,target=/root/.local/share/pnpm/store \
+    pnpm install --frozen-lockfile --filter lanqin-email-web...
+COPY apps/web apps/web
+RUN pnpm --dir apps/web run build
 
 FROM nginx:1.27-alpine
 COPY --from=build /src/apps/web/dist /usr/share/nginx/html