fix: 修复博客图片加载失败（掘金防盗链）

- 将《Git使用教学》中的掘金外链图片下载至 source/images/ 并替换为站内路径
- _config.yml 注入 no-referrer meta 作为兜底方案
- 新增 tools/download-juejin-images.js 批量下载/替换脚本

tools/download-juejin-images.ps1

@@ -0,0 +1,61 @@
+# 下载 Markdown 中的掘金外链图片到 source/images/，并替换链接为站内路径
+param(
+    [string]$MdPath = "c:/Users/Administrator/Desktop/新建文件夹/blog/source/_posts/Git使用教学.md",
+    [string]$OutDir = "c:/Users/Administrator/Desktop/新建文件夹/blog/source/images"
+)
+
+$ErrorActionPreference = "Stop"
+New-Item -ItemType Directory -Force -Path $OutDir | Out-Null
+
+$content = Get-Content -Path $MdPath -Raw -Encoding UTF8
+
+# 匹配 ![alt](url) 中的掘金图片地址
+$pattern = '!\[[^\]]*\]\((https://p3-juejin\.byteimg\.com/[^)\s]+)\)'
+$imgMatches = [regex]::Matches($content, $pattern)
+
+$map = @{}   # url -> /images/xxx.webp
+$count = 0
+$failed = @()
+
+foreach ($m in $imgMatches) {
+    $url = $m.Groups[1].Value
+    if ($map.ContainsKey($url)) { continue }
+
+    # 用 URL 路径最后一段中 "~" 之前的部分作为文件名（即图片 hash）
+    $seg = ($url -split '/')[-1]
+    $hash = ($seg -split '~')[0]
+    if ([string]::IsNullOrEmpty($hash)) {
+        $failed += "无法解析文件名: $url"
+        continue
+    }
+    $file = $hash + '.webp'
+    $dest = Join-Path $OutDir $file
+
+    try {
+        curl.exe -s -L --max-time 30 -o $dest $url
+        if ((Test-Path $dest) -and ((Get-Item $dest).Length -gt 0)) {
+            $map[$url] = '/images/' + $file
+            $count++
+            Write-Host "[OK] $file  <-  $url"
+        } else {
+            $failed += "下载为空: $url"
+        }
+    } catch {
+        $failed += "下载异常: $url -> $_"
+    }
+}
+
+# 替换 Markdown 中的外链
+foreach ($kv in $map.GetEnumerator()) {
+    $content = $content.Replace($kv.Key, $kv.Value)
+}
+
+# 写回（UTF-8 无 BOM）
+[System.IO.File]::WriteAllText($MdPath, $content, [System.Text.UTF8Encoding]::new($false))
+
+Write-Host ""
+Write-Host "完成：成功下载 $count 张，失败 $($failed.Count) 张"
+if ($failed.Count -gt 0) {
+    Write-Host "失败列表："
+    $failed | ForEach-Object { Write-Host "  - $_" }
+}