feat(web): 增强任务治理与系统诊断能力

新增任务持久化、筛选分页、取消任务、健康检查与 AI 输入校验，并完善前端历史管理交互与容错重试机制。补充对应单元测试，提升系统稳定性和可运维性。

src/test/java/com/svnlog/web/service/AiInputValidatorTest.java

@@ -0,0 +1,36 @@
+package com.svnlog.web.service;
+
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Arrays;
+import java.util.Collections;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class AiInputValidatorTest {
+
+    @Test
+    public void shouldRejectEmptyListWhenValidatingInputFiles() {
+        AiInputValidator validator = new AiInputValidator();
+        Assertions.assertThrows(IllegalArgumentException.class, () -> validator.validate(Collections.<Path>emptyList()));
+    }
+
+    @Test
+    public void shouldRejectNonMarkdownFileWhenValidatingInputFiles() throws Exception {
+        AiInputValidator validator = new AiInputValidator();
+        Path temp = Files.createTempFile("ai-input", ".txt");
+        Files.write(temp, "abc".getBytes(StandardCharsets.UTF_8));
+        Assertions.assertThrows(IllegalArgumentException.class, () -> validator.validate(Arrays.asList(temp)));
+    }
+
+    @Test
+    public void shouldAcceptSmallMarkdownFilesWhenValidatingInputFiles() throws Exception {
+        AiInputValidator validator = new AiInputValidator();
+        Path temp = Files.createTempFile("ai-input", ".md");
+        Files.write(temp, "# title".getBytes(StandardCharsets.UTF_8));
+        validator.validate(Arrays.asList(temp));
+        Assertions.assertTrue(true);
+    }
+}