feat: initial release of pengzhan.dev personal editorial blog platform

- Editorial web platform built with Node.js, Express, EJS, and Vanilla CSS
- Markdown content engine with YAML frontmatter, bilingual variants, and hot-reload watcher
- Unified SQLite with FTS5 search indexing, query logging, and schema filters
- Centered editorial post layout with margin-docked left TOC and mobile bottom sheet
- WordPress-grade comment system with moderation dashboard and bulk operations under /guanli
- Complete SEO suite (JSON-LD structured data, RSS/Atom feeds, XML sitemap, robots.txt)
- CI/CD workflows for linting, security audits (Gitleaks), automated tests, and Docker releases

sample-content/posts/ai-can-change-coding-for-kids/images/cover.svg

@@ -0,0 +1,41 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 600 600" width="100%" height="100%">
+  <defs>
+    <linearGradient id="kidBg" x1="0%" y1="0%" x2="100%" y2="100%">
+      <stop offset="0%" stop-color="#fed7aa"/>
+      <stop offset="100%" stop-color="#fb923c"/>
+    </linearGradient>
+    <filter id="kidShadow" x="-10%" y="-10%" width="120%" height="120%">
+      <feDropShadow dx="0" dy="6" stdDeviation="10" flood-opacity="0.15"/>
+    </filter>
+  </defs>
+  <rect width="600" height="600" fill="url(#kidBg)" rx="32"/>
+
+  <!-- Creative Building Blocks / Robot Icon -->
+  <g transform="translate(300, 250)" filter="url(#kidShadow)">
+    <rect x="-90" y="-80" width="180" height="150" rx="24" fill="#ffffff"/>
+    <!-- Robot antenna -->
+    <line x1="0" y1="-80" x2="0" y2="-120" stroke="#ffffff" stroke-width="8" stroke-linecap="round"/>
+    <circle cx="0" cy="-125" r="14" fill="#ea580c"/>
+    <!-- Eyes -->
+    <circle cx="-40" cy="-15" r="16" fill="#0284c7"/>
+    <circle cx="40" cy="-15" r="16" fill="#0284c7"/>
+    <!-- Smile -->
+    <path d="M -40 30 Q 0 60 40 30" stroke="#ea580c" stroke-width="8" stroke-linecap="round" fill="none"/>
+  </g>
+
+  <!-- Educational Blocks -->
+  <g transform="translate(180, 420)" filter="url(#kidShadow)">
+    <rect x="0" y="0" width="60" height="60" rx="12" fill="#38bdf8"/>
+    <text x="30" y="42" text-anchor="middle" fill="#ffffff" font-family="-apple-system, sans-serif" font-size="32" font-weight="900">A</text>
+  </g>
+  <g transform="translate(260, 400)" filter="url(#kidShadow)">
+    <rect x="0" y="0" width="60" height="60" rx="12" fill="#ec4899"/>
+    <text x="30" y="42" text-anchor="middle" fill="#ffffff" font-family="-apple-system, sans-serif" font-size="32" font-weight="900">I</text>
+  </g>
+  <g transform="translate(340, 420)" filter="url(#kidShadow)">
+    <rect x="0" y="0" width="60" height="60" rx="12" fill="#10b981"/>
+    <text x="30" y="42" text-anchor="middle" fill="#ffffff" font-family="-apple-system, sans-serif" font-size="32" font-weight="900">&lt;&gt;</text>
+  </g>
+
+  <text x="300" y="530" text-anchor="middle" fill="#7c2d12" font-family="-apple-system, sans-serif" font-size="28" font-weight="800">Coding for Kids</text>
+</svg>