feat: replace unified loading approach with global loading provider and refactor loading handling across components

- Introduced GlobalLoadingProvider to manage a consistent loading overlay across the application.
- Replaced existing loading implementations with useGlobalLoadingEffect hook for better control and to prevent animation resets.
- Updated components such as LoginPage, AuthCallbackPage, and DashboardLayout to utilize the new global loading mechanism.
- Removed UnifiedLoadingScreen component to streamline loading management and enhance user experience.

surfsense_web/components/providers/ElectricProvider.tsx

@@ -4,7 +4,7 @@ import { useAtomValue } from "jotai";
 import { useTranslations } from "next-intl";
 import { useEffect, useRef, useState } from "react";
 import { currentUserAtom } from "@/atoms/user/user-query.atoms";
-import { UnifiedLoadingScreen } from "@/components/ui/unified-loading-screen";
+import { useGlobalLoadingEffect } from "@/hooks/use-global-loading";
 import { getBearerToken } from "@/lib/auth-utils";
 import {
 	cleanupElectric,
@@ -113,19 +113,21 @@ export function ElectricProvider({ children }: ElectricProviderProps) {
 	// This prevents showing loading screen for unauthenticated users on homepage
 	const hasToken = typeof window !== "undefined" && !!getBearerToken();
 
+	// Determine if we should show loading
+	const shouldShowLoading = hasToken && isUserLoaded && !!user?.id && !electricClient && !error;
+
+	// Use global loading hook with ownership tracking - prevents flash during transitions
+	useGlobalLoadingEffect(shouldShowLoading, t("initializing"), "default");
+
 	// For non-authenticated pages (like landing page), render immediately with null context
 	// Also render immediately if user query failed (e.g., token expired)
 	if (!hasToken || !isUserLoaded || !user?.id || isUserError) {
 		return <ElectricContext.Provider value={null}>{children}</ElectricContext.Provider>;
 	}
 
-	// Show loading state while initializing for authenticated users
+	// Return children with null context while initializing - the global provider handles the loading UI
 	if (!electricClient && !error) {
-		return (
-			<ElectricContext.Provider value={null}>
-				<UnifiedLoadingScreen variant="default" message={t("initializing")} />
-			</ElectricContext.Provider>
-		);
+		return <ElectricContext.Provider value={null}>{children}</ElectricContext.Provider>;
 	}
 
 	// If there's an error, still render but warn