feat: 页面模板差异化改进 + 配置优化 + 兼容清理 (#29)

- 首页判定：navigation 第一项
- 模板：page/projects/articles/bookmarks/search-results
- bookmarks：update: YYYY-MM-DD | from: git|mtime
- articles：RSS 聚合只读条目 + 分类聚合 + 影子写回结构
- projects：repo 卡片 + 可选热力图 + 自动抓取元信息
- 工作流：构建前 sync + schedule 定时刷新
- 移除兼容：config.yml/config.yaml、navigation.yml、home 特例
- 迁移说明：config/update-instructions.md

templates/components/page-header.hbs

@@ -0,0 +1,36 @@
+{{!-- page-header.hbs - 统一页面标题区（可选显示书签页内容更新时间） --}}
+<div class="welcome-section{{#ifCond projectsMeta '&&' projectsMeta.heatmap}} welcome-section-with-side{{/ifCond}}">
+    <div class="welcome-section-main">
+        {{#ifEquals pageId @root.homePageId}}
+            <h2 data-editable="profile-title">{{title}}</h2>
+            <h3 data-editable="profile-subtitle">{{subtitle}}</h3>
+        {{else}}
+            <div class="welcome-title-row">
+                <h2 data-editable="page-title">{{title}}</h2>
+                {{#if pageMeta}}
+                {{#if pageMeta.updatedAt}}
+                    <span class="page-updated-inline" title="{{pageMeta.updatedAt}}">
+                        update: {{formatDate pageMeta.updatedAt "YYYY-MM-DD"}} | from: {{pageMeta.updatedAtSource}}
+                    </span>
+                {{/if}}
+                {{/if}}
+            </div>
+            <p class="subtitle" data-editable="page-subtitle">{{subtitle}}</p>
+        {{/ifEquals}}
+    </div>
+
+    {{#if projectsMeta}}
+    {{#if projectsMeta.heatmap}}
+    <div class="welcome-section-side">
+        <div class="heatmap-container" title="我的 GitHub 贡献热力图">
+            <a href="{{projectsMeta.heatmap.profileUrl}}" target="_blank" rel="noopener">
+                <img class="heatmap-img"
+                     src="{{projectsMeta.heatmap.imageUrl}}"
+                     alt="Github Chart"
+                     loading="lazy" />
+            </a>
+        </div>
+    </div>
+    {{/if}}
+    {{/if}}
+</div>