feat: 修复仪表盘数据管线 — 补充应用发布种子数据 + 修复limit参数解析 + LDAP认证集成 + User类型完善

后端改进:
- 修复 dashboard/recent-alerts 的 limit 参数解析 (原代码错误地将数字解析为日期)
- 为 dashboard/recent-releases 添加 limit 参数解析支持
- 新增 generateAppReleases 种子数据生成函数 (10条应用发布记录)
- 修复 AlertEvent 的 rule_name/rule_id/severity 数据一致性
- 添加 go-ldap/ldap/v3 依赖并集成 LDAP 认证处理器
- 添加 seed.go 自动种子数据初始化 (admin用户+LDAP配置)
- User model 添加 AuthSource/LDAPConfig 字段

前端改进:
- 修复 User 类型定义以匹配后端 API (real_name/is_admin/auth_source等)
- 修复 Header.tsx 的 real_name 属性引用导致 TypeScript 编译错误
- 统一 API 服务层、暗色主题样式、组件联调优化

验证:
- go build ./... 编译通过
- npm run build 构建通过
- 仪表盘发布历史、告警消息等区域数据正常展示
- 健康检查 /health 正常

frontend/src/hooks/useTheme.tsx

@@ -0,0 +1,101 @@
+import { createContext, useContext, useState, useCallback, useMemo, useEffect } from 'react';
+
+export type Theme =
+  | 'ocean-deep'
+  | 'light-professional'
+  | 'midnight-purple'
+  | 'pine-green'
+  | 'orange-vitality';
+
+export interface ThemeOption {
+  id: Theme;
+  name: string;
+  description: string;
+  isDark: boolean;
+  primaryColor: string;
+}
+
+export const THEME_OPTIONS: ThemeOption[] = [
+  { id: 'ocean-deep', name: '深海蓝', description: '专业稳重的深蓝色调', isDark: true, primaryColor: '#3b82f6' },
+  { id: 'light-professional', name: '明亮白', description: '清爽干净的浅色主题', isDark: false, primaryColor: '#2563eb' },
+  { id: 'midnight-purple', name: '午夜紫', description: '神秘优雅的紫色调', isDark: true, primaryColor: '#a855f7' },
+  { id: 'pine-green', name: '松林绿', description: '自然清新的绿色主题', isDark: true, primaryColor: '#22c55e' },
+  { id: 'orange-vitality', name: '活力橙', description: '温暖活力的橙色主题', isDark: true, primaryColor: '#f97316' },
+];
+
+const THEME_ORDER: Theme[] = THEME_OPTIONS.map((o) => o.id);
+const DEFAULT_THEME: Theme = 'ocean-deep';
+const STORAGE_KEY = 'aiops-theme';
+
+// Backward compatibility: map old theme names to new ones
+function migrateLegacyTheme(value: string | null): Theme | null {
+  if (value === 'dark') return 'ocean-deep';
+  if (value === 'light') return 'light-professional';
+  return null;
+}
+
+interface ThemeContextType {
+  theme: Theme;
+  toggleTheme: () => void;
+  setTheme: (theme: Theme) => void;
+}
+
+const ThemeContext = createContext<ThemeContextType | null>(null);
+
+function getInitialTheme(): Theme {
+  if (typeof window === 'undefined') return DEFAULT_THEME;
+  const stored = localStorage.getItem(STORAGE_KEY);
+  const migrated = migrateLegacyTheme(stored);
+  if (migrated) {
+    // Persist the migrated value so we don't migrate every time
+    localStorage.setItem(STORAGE_KEY, migrated);
+    return migrated;
+  }
+  if (stored && THEME_ORDER.includes(stored as Theme)) {
+    return stored as Theme;
+  }
+  return DEFAULT_THEME;
+}
+
+function applyTheme(theme: Theme) {
+  document.documentElement.setAttribute('data-theme', theme);
+}
+
+export function ThemeProvider({ children }: { children: React.ReactNode }) {
+  const [theme, setThemeState] = useState<Theme>(getInitialTheme);
+
+  useEffect(() => {
+    applyTheme(theme);
+  }, [theme]);
+
+  const toggleTheme = useCallback(() => {
+    setThemeState((prev) => {
+      const idx = THEME_ORDER.indexOf(prev);
+      const next = THEME_ORDER[(idx + 1) % THEME_ORDER.length];
+      localStorage.setItem(STORAGE_KEY, next);
+      return next;
+    });
+  }, []);
+
+  const setTheme = useCallback((t: Theme) => {
+    localStorage.setItem(STORAGE_KEY, t);
+    setThemeState(t);
+  }, []);
+
+  const value = useMemo(
+    () => ({
+      theme,
+      toggleTheme,
+      setTheme,
+    }),
+    [theme, toggleTheme, setTheme]
+  );
+
+  return <ThemeContext.Provider value={value}>{children}</ThemeContext.Provider>;
+}
+
+export function useTheme(): ThemeContextType {
+  const ctx = useContext(ThemeContext);
+  if (!ctx) throw new Error('useTheme must be used within ThemeProvider');
+  return ctx;
+}