fix(pages): 修复 TypeScript 错误、硬编码字符串，移除死代码

- 修复 LiveClock.tsx CopyButton size 属性类型错误 (small → sm)
- 修复 ToolCard.tsx 紫色 RGB 值拼写错误 (147,51,2 purple → 147,51,232)
- 替换 4 处硬编码中文为 i18n 调用 (StorageCleaner, JsonTools)
- MarkdownToHtml 预览链接色改为 CSS 变量以支持暗黑模式
- 移除 Base64Converter 中已被 Base64ConverterSection 替代的死代码
  (FileMode.tsx, ImageMode.tsx 及其测试文件)
- 更新 README.md 移除对已删除文件的引用

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

pages/JsonTools/JsonConvertSection.tsx

@@ -133,7 +133,7 @@ export default function JsonConvertSection({
         /* 5. 空状态提示容器：完美的中性虚线引导，不喧宾夺主 */
         <div className="p-8 rounded-xl bg-muted/30 border border-dashed border-border/80 text-center flex flex-col items-center justify-center min-h-[120px] select-none">
           <p className="text-xs font-semibold text-muted-foreground/80 tracking-wide max-w-[240px] leading-relaxed">
-            {error ? '请修正上方 JSON 的语法错误以激活流式转换' : t(`jsonFormat:${pk}EmptyHint`)}
+            {error ? t('jsonFormat:fixErrorHint') : t(`jsonFormat:${pk}EmptyHint`)}
           </p>
         </div>
       )}

pages/JsonTools/JsonFormatSection.tsx

@@ -160,7 +160,7 @@ export default function JsonFormatSection() {
         /* 空状态指示引导区 */
         <div className="p-8 rounded-xl bg-muted/30 border border-dashed border-border/80 text-center flex flex-col items-center justify-center min-h-[120px] select-none">
           <p className="text-xs font-semibold text-muted-foreground/80 tracking-wide max-w-[240px] leading-relaxed">
-            {error ? '请修正上方 JSON 语法错误以开启实时流式格式化' : t('jsonFormat:emptyHint')}
+            {error ? t('jsonFormat:fixErrorHint') : t('jsonFormat:emptyHint')}
           </p>
         </div>
       )}

pages/JsonTools/index.tsx

@@ -182,9 +182,7 @@ export default function Index() {
           ) : (
             <div className="p-8 rounded-xl bg-muted/30 border border-dashed border-border/80 text-center flex flex-col items-center justify-center min-h-[140px]">
               <p className="text-xs font-semibold text-muted-foreground/80 tracking-wide max-w-[260px] leading-relaxed">
-                {leftError || rightError
-                  ? '请修正上方 JSON 的语法错误以开启实时流式比对'
-                  : t('jsonDiff:emptyHint')}
+                {leftError || rightError ? t('jsonDiff:fixErrorHint') : t('jsonDiff:emptyHint')}
               </p>
             </div>
           )}