feat(Jwt): 重构 JWT 组件，新增常量和结果视图

- 新增 constants.ts 文件，定义 JWT 输入占位符和配置常量，提升代码可读性。
- 删除 JwtSection 组件，重构为 JwtResultView 组件，简化结果展示逻辑。
- 更新 index.tsx，使用 JwtResultView 组件替代原有的 JWT 结果展示方式，优化页面结构。

src/pages/Jwt/index.tsx

@@ -1,66 +1,26 @@
 import TextInputArea from '@/components/TextInputArea';
-import { CopyButton } from '@/components/CopyButton';
-import EmptyPlaceholder from '@/components/EmptyPlaceholder';
-import JwtSection from './JwtSection';
+import JwtResultView from './components/JwtResultView';
+import { JWT_INPUT_PLACEHOLDER } from './constants';
 import { useJwt } from './useJwt';
 
 export default function Index() {
   const { jwtInput, result, handleChange, handleClear } = useJwt();
 
   return (
-    <div className="p-4 w-full flex flex-col space-y-4 select-none">
-      <div className="flex flex-col gap-4">
-        <TextInputArea
-          minRows={5}
-          maxRows={10}
-          placeholder={'在此粘贴 JWT 令牌 (Encoded JWT)...'}
-          value={jwtInput}
-          onChange={handleChange}
-          allowCopy={true}
-          showClear={true}
-          externalError={result?.error || undefined}
-          onClear={handleClear}
-        />
+    <div className="p-4 w-full flex flex-col gap-4 select-none">
+      <TextInputArea
+        minRows={5}
+        maxRows={10}
+        placeholder={JWT_INPUT_PLACEHOLDER}
+        value={jwtInput}
+        onChange={handleChange}
+        allowCopy={true}
+        showClear={true}
+        externalError={result?.error || undefined}
+        onClear={handleClear}
+      />
 
-        {result && !result.error && (
-          <div className="flex flex-col gap-4">
-            <JwtSection
-              title={'HEADER: 算法 & 令牌类型'}
-              content={result.header}
-              colorClass="text-[#fb015b] dark:text-rose-400"
-              borderClass="border-[#fb015b]/20 dark:border-rose-500/20"
-              bgClass="bg-[#fb015b]/5 dark:bg-rose-500/5"
-            />
-
-            <JwtSection
-              title={'PAYLOAD: 数据'}
-              content={result.payload}
-              colorClass="text-[#a03aff] dark:text-purple-400"
-              borderClass="border-[#a03aff]/20 dark:border-purple-500/20"
-              bgClass="bg-[#a03aff]/5 dark:bg-purple-500/5"
-            />
-
-            <div className="p-4 rounded-xl border border-border bg-secondary/40 shadow-sm">
-              <div className="flex justify-between items-center mb-2">
-                <span className="text-xs font-bold tracking-wider text-muted-foreground/90 uppercase">
-                  {'签名'}
-                </span>
-                <CopyButton
-                  text={result.signature || ''}
-                  className="h-6 w-6 rounded-md border text-muted-foreground"
-                />
-              </div>
-              <span className="block text-xs font-mono break-all text-foreground/80 bg-muted/30 dark:bg-muted/10 p-3 rounded-lg border border-border/50 leading-relaxed select-text">
-                {result.signature || '无签名'}
-              </span>
-            </div>
-          </div>
-        )}
-
-        {result?.error && (
-          <EmptyPlaceholder className="p-6 min-h-0">{'无效的 JSON 格式'}</EmptyPlaceholder>
-        )}
-      </div>
+      {result && !result.error && <JwtResultView result={result} />}
     </div>
   );
 }