feat(phone-image): 添加字号倍数控制功能

- CSS: 新增 --pi-font-scale 变量,全量 font-size 支持 calc 缩放
- JS: config.fontScale 影响分页计算,applyFontScale() 同步CSS变量
- HTML: 渲染预览区 Slider 控件(0.5x~2.0x),拖动即时预览,松手完整渲染
- 后端: PhoneImage.php 新增 fontScale 配置字段和校验
- 所有保存路径(autoSave/save/generate)包含 fontScale 持久化

view/admin/post/phone_image.html

@@ -165,7 +165,15 @@
 
         <!-- 中间：渲染预览区 -->
         <div class="render-preview-area">
-            <div class="preview-header">渲染预览</div>
+            <div class="preview-header">
+                <span>渲染预览</span>
+                <div style="display:inline-flex;align-items:center;gap:8px;float:right;">
+                    <span style="font-size:12px;color:#666;">字号</span>
+                    <input type="range" id="font-scale-slider" min="0.5" max="2.0" step="0.1" value="1.0"
+                           style="width:100px;vertical-align:middle;">
+                    <span id="font-scale-value" style="font-size:12px;color:#1890ff;min-width:32px;">1.0x</span>
+                </div>
+            </div>
             <div id="render-preview"></div>
         </div>
 
@@ -195,7 +203,8 @@
             // 当前排版配置（从设置弹框维护）
             var currentConfig = {
                 size: 'xiaohongshu',
-                watermark: ''
+                watermark: '',
+                fontScale: 1
             };
 
             var postData = {
@@ -215,12 +224,14 @@
             var initConfig = {
                 size: savedConfig.size || 'xiaohongshu',
                 watermark: savedConfig.watermark || '',
-                pageAlignments: savedConfig.pageAlignments || {}
+                pageAlignments: savedConfig.pageAlignments || {},
+                fontScale: savedConfig.fontScale || 1
             };
 
             // 同步当前配置
             currentConfig.size = initConfig.size;
             currentConfig.watermark = initConfig.watermark;
+            currentConfig.fontScale = initConfig.fontScale;
 
             // ========== wangeditor 初始化 ==========
             var E = window.wangEditor;
@@ -331,6 +342,31 @@
             // 初始同步预览区
             PhoneImageEngine.syncPreview();
 
+            // 字号倍数 Slider
+            var $slider = $('#font-scale-slider');
+            var $scaleValue = $('#font-scale-value');
+
+            // 拖动中: 仅更新CSS变量和显示值,不触发html2canvas
+            $slider.on('input', function() {
+                var val = parseFloat($(this).val());
+                $scaleValue.text(val.toFixed(1) + 'x');
+                currentConfig.fontScale = val;
+                document.documentElement.style.setProperty('--pi-font-scale', val);
+                PhoneImageEngine.updateConfig({ fontScale: val });
+            });
+
+            // 松手后: 触发完整渲染(重新分页 + html2canvas截图)
+            $slider.on('change', function() {
+                var val = parseFloat($(this).val());
+                doRender({ fontScale: val });
+            });
+
+            // 初始化时更新 Slider 显示值
+            if (initConfig.fontScale && initConfig.fontScale !== 1) {
+                $slider.val(initConfig.fontScale);
+                $scaleValue.text(parseFloat(initConfig.fontScale).toFixed(1) + 'x');
+            }
+
             // ========== 设置弹框 ==========
             $('#btn-settings').click(function () {
                 var settingsHtml = '<div class="settings-form" style="padding:20px 20px 0;">';
@@ -451,6 +487,7 @@
                     PhoneImageEngine.saveConfig(postData.postId, {
                         size: currentConfig.size,
                         watermark: currentConfig.watermark,
+                        fontScale: currentConfig.fontScale || 1,
                         content_html: PhoneImageEngine.getContentHtml()
                     }, saveConfigUrl).then(function (data) {
                         if (data.output_id) lastOutputId = data.output_id;
@@ -476,6 +513,7 @@
                 PhoneImageEngine.saveConfig(postData.postId, {
                     size: currentConfig.size,
                     watermark: currentConfig.watermark,
+                    fontScale: currentConfig.fontScale || 1,
                     content_html: PhoneImageEngine.getContentHtml()
                 }, saveConfigUrl).then(function (data) {
                     if (data.output_id) lastOutputId = data.output_id;
@@ -499,6 +537,7 @@
                 PhoneImageEngine.saveImages(postData.postId, {
                     size: currentConfig.size,
                     watermark: currentConfig.watermark,
+                    fontScale: currentConfig.fontScale || 1,
                     content_html: PhoneImageEngine.getContentHtml()
                 }).then(function (data) {
                     if (data.output_id) {
@@ -584,10 +623,16 @@
                     if (cfg.size) historyConfig.size = cfg.size;
                     if (cfg.watermark !== undefined) historyConfig.watermark = cfg.watermark;
                     if (cfg.pageAlignments) historyConfig.pageAlignments = cfg.pageAlignments;
+                    if (cfg.fontScale !== undefined) historyConfig.fontScale = cfg.fontScale;
 
                     // 同步当前配置
                     if (cfg.size) currentConfig.size = cfg.size;
                     if (cfg.watermark !== undefined) currentConfig.watermark = cfg.watermark;
+                    if (cfg.fontScale !== undefined) {
+                        currentConfig.fontScale = cfg.fontScale;
+                        $slider.val(cfg.fontScale);
+                        $scaleValue.text(parseFloat(cfg.fontScale).toFixed(1) + 'x');
+                    }
 
                     lastOutputId = outputId;
                     layer.closeAll();