feat(notify-email): composite action 通过 SMTP 发邮件 + lint workflow

- notify-email 用 curl smtps:// 协议，163/126 兼容
- self-mail 模式：USER/TO 可同账号
- 失败时 ::warning:: 不阻塞
- lint workflow: yamllint 验证 action.yml 语法

.gitea/workflows/lint.yml

@@ -0,0 +1,19 @@
+name: lint
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+jobs:
+  yamllint:
+    runs-on: ubuntu-latest
+    container:
+      image: docker.io/catthehacker/ubuntu:act-latest
+    steps:
+      # runner 默认已 clone 当前仓库（ci-actions 自身）到 step 工作目录
+      # 无需 actions/checkout（也避免拉 github.com）
+      - name: Install yamllint
+        run: |
+          apt-get update && apt-get install -y yamllint
+      - name: Run yamllint
+        run: yamllint .