feat(typesetting): Wave 1 - 对齐修复+底部对齐、封面页字号豁免、字号UI改造

- 修复对齐按钮缺少click handler的缺陷，新增事件委托
- 三态对齐切换: 居顶(↑) -> 居中(↕) -> 居底(↓)
- 封面页和尾页通过CSS变量重置不受全局fontScale影响
- 字号控制从slider改为dropdown+自定义输入，预设0.5/0.8/1.0/1.2/1.5/2.0

public/static/css/phone-image-templates.css

@@ -112,6 +112,7 @@
 
 /* --- 封面页/首页 --- */
 .page-cover {
+    --pi-font-scale: 1 !important;
     display: flex;
     flex-direction: column;
     justify-content: center;
@@ -335,6 +336,7 @@
 
 /* --- 总结页/尾页 --- */
 .page-summary {
+    --pi-font-scale: 1 !important;
     display: flex;
     flex-direction: column;
     justify-content: center;
@@ -417,6 +419,12 @@
     justify-content: center;
 }
 
+.page-body.valign-bottom .page-content {
+    display: flex;
+    flex-direction: column;
+    justify-content: flex-end;
+}
+
 /* ============================================
    Content Flow (中间栏内容流)
    所有元素按实际尺寸纵向排列

public/static/js/phone-image.js

@@ -897,7 +897,12 @@ var PhoneImageEngine = (function () {
     function generateContentPage(blocks, pageNum, sizeConfig, isLast) {
         // 读取逐页对齐配置
         var alignment = (config.pageAlignments && config.pageAlignments[pageNum]) || 'top';
-        var valignClass = alignment === 'center' ? ' valign-center' : '';
+        var valignClass = '';
+        if (alignment === 'center') {
+            valignClass = ' valign-center';
+        } else if (alignment === 'bottom') {
+            valignClass = ' valign-bottom';
+        }
 
         var html = '<div class="phone-image-page page-body' + valignClass + '" style="width:' +
             sizeConfig.width + 'px;height:' + sizeConfig.height + 'px;">';
@@ -1230,8 +1235,11 @@ var PhoneImageEngine = (function () {
                 var pageNum = pages[i].pageNum || (i);
                 var currentAlign = (config.pageAlignments && config.pageAlignments[pageNum]) || 'top';
                 var isActiveCenter = currentAlign === 'center';
-                var $toggle = $('<button class="thumb-alignment-toggle' + (isActiveCenter ? ' active-center' : '') + '" data-page-index="' + i + '" data-page-num="' + pageNum + '">' +
-                    (isActiveCenter ? '\u2195' : '\u2191') +
+                var isActiveBottom = currentAlign === 'bottom';
+                var activeClass = isActiveCenter ? ' active-center' : (isActiveBottom ? ' active-bottom' : '');
+                var symbol = isActiveCenter ? '\u2195' : (isActiveBottom ? '\u2193' : '\u2191');
+                var $toggle = $('<button class="thumb-alignment-toggle' + activeClass + '" data-page-index="' + i + '" data-page-num="' + pageNum + '">' +
+                    symbol +
                     '</button>');
                 $item.append($toggle);
             }
@@ -1580,6 +1588,26 @@ var PhoneImageEngine = (function () {
         return div.innerHTML;
     }
 
+    // ===== 对齐按钮事件委托 =====
+    $(document).on('click', '.thumb-alignment-toggle', function () {
+        var $btn = $(this);
+        var pageNum = parseInt($btn.attr('data-page-num'), 10);
+        var currentAlign = (config.pageAlignments && config.pageAlignments[pageNum]) || 'top';
+
+        // 三态循环: top -> center -> bottom -> top
+        var nextAlign;
+        if (currentAlign === 'top') {
+            nextAlign = 'center';
+        } else if (currentAlign === 'center') {
+            nextAlign = 'bottom';
+        } else {
+            nextAlign = 'top';
+        }
+
+        setPageAlignment(pageNum, nextAlign);
+        render();
+    });
+
     // ===== 公开API =====
     return {
         init: init,