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 .

notify-email/README.md

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+# notify-email
+
+通过 SMTP 发送 Gitea Actions run 结果邮件。**已验证兼容 163 / 126 邮箱**。
+
+## Inputs
+
+| 名称 | 必填 | 默认 | 说明 |
+|---|---|---|---|
+| `smtp_host` | ✅ | — | 例：`smtp.163.com` |
+| `smtp_port` | ❌ | `465` | SSL 端口 |
+| `smtp_user` | ✅ | — | 完整邮箱地址 |
+| `smtp_pass` | ✅ | — | 授权码（业务 repo 配 Gitea secret） |
+| `from` | ❌ | = `smtp_user` | 发件人 |
+| `to` | ✅ | — | 收件人，多个用逗号 |
+| `subject` | ✅ | — | 邮件主题 |
+| `body` | ✅ | — | 邮件正文（纯文本） |
+
+## 使用示例
+
+```yaml
+- uses: gitea_admin/ci-actions/notify-email@v1
+  with:
+    smtp_host: smtp.163.com
+    smtp_user: ${{ secrets.EMAIL_USER }}
+    smtp_pass: ${{ secrets.EMAIL_SMTP_PASS }}
+    to: ${{ secrets.EMAIL_TO }}
+    subject: "[gitea-ci] ${{ github.repository }} - ${{ needs.build.result }}"
+    body: |
+      repository: ${{ github.repository }}
+      workflow: ${{ github.workflow }}
+      status: ${{ needs.build.result }}
+      url: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}
+```
+
+## 安全
+
+`smtp_pass` **必须**通过 Gitea secret 传入，**不要**直接写在 workflow 里。
+
+## 失败处理
+
+邮件发送失败时输出 `::warning::Email send failed (non-fatal)`，**不阻塞**调用方 job。

notify-email/action.yml

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+name: 'Notify Email'
+description: 'Send Gitea Actions run result via SMTP (163/126 compatible)'
+author: 'gitea_admin'
+
+inputs:
+  smtp_host:
+    description: 'SMTP host (e.g. smtp.126.com)'
+    required: true
+  smtp_port:
+    description: 'SMTP SSL port'
+    required: false
+    default: '465'
+  smtp_user:
+    description: 'SMTP user (full email address)'
+    required: true
+  smtp_pass:
+    description: 'SMTP authorization code'
+    required: true
+  from:
+    description: 'From address'
+    required: false
+    default: ${{ inputs.smtp_user }}
+  to:
+    description: 'Recipient(s), comma separated'
+    required: true
+  subject:
+    description: 'Email subject'
+    required: true
+  body:
+    description: 'Email body (plain text)'
+    required: true
+
+runs:
+  using: 'composite'
+  steps:
+    - name: Send email via SMTP
+      shell: bash
+      env:
+        SMTP_HOST: ${{ inputs.smtp_host }}
+        SMTP_PORT: ${{ inputs.smtp_port }}
+        SMTP_USER: ${{ inputs.smtp_user }}
+        SMTP_PASS: ${{ inputs.smtp_pass }}
+        FROM_ADDR: ${{ inputs.from }}
+        TO_ADDR: ${{ inputs.to }}
+        SUBJECT: ${{ inputs.subject }}
+        BODY: ${{ inputs.body }}
+      run: |
+        set -u
+        # 构造 --mail-rcpt 参数（每个收件人一个）
+        RCPT_ARGS=""
+        IFS=','
+        for addr in $TO_ADDR; do
+          RCPT_ARGS="$RCPT_ARGS --mail-rcpt $(printf '%s' "$addr" | sed 's/^[[:space:]]*//;s/[[:space:]]*$//')"
+        done
+        unset IFS
+        # shellcheck disable=SC2086
+        if ! printf '%s' "$BODY" | curl -fsS --ssl \
+            --url "smtps://${SMTP_HOST}:${SMTP_PORT}" \
+            --user "${SMTP_USER}:${SMTP_PASS}" \
+            --mail-from "${FROM_ADDR}" \
+            $RCPT_ARGS \
+            -H "Subject: ${SUBJECT}" \
+            -H "From: ${FROM_ADDR}" \
+            -H "To: ${TO_ADDR}" \
+            -H "Content-Type: text/plain; charset=UTF-8" \
+            --max-time 15 --retry 2 \
+            --upload-file -; then
+          echo "::warning::Email send failed (non-fatal)"
+        fi