Restructure frontend code to allow for extensions (#4721)

# Description of Changes
Move frontend code into `core` folder and add infrastructure for
`proprietary` folder to include premium, non-OSS features

frontend/src/core/contexts/AppConfigContext.tsx

@@ -0,0 +1,107 @@
+import React, { createContext, useContext, useState, useEffect } from 'react';
+import { useRequestHeaders } from '@app/hooks/useRequestHeaders';
+
+export interface AppConfig {
+  baseUrl?: string;
+  contextPath?: string;
+  serverPort?: number;
+  appName?: string;
+  appNameNavbar?: string;
+  homeDescription?: string;
+  languages?: string[];
+  enableLogin?: boolean;
+  enableAlphaFunctionality?: boolean;
+  enableAnalytics?: boolean | null;
+  enablePosthog?: boolean | null;
+  enableScarf?: boolean | null;
+  premiumEnabled?: boolean;
+  premiumKey?: string;
+  termsAndConditions?: string;
+  privacyPolicy?: string;
+  cookiePolicy?: string;
+  impressum?: string;
+  accessibilityStatement?: string;
+  runningProOrHigher?: boolean;
+  runningEE?: boolean;
+  license?: string;
+  SSOAutoLogin?: boolean;
+  serverCertificateEnabled?: boolean;
+  error?: string;
+}
+
+interface AppConfigContextValue {
+  config: AppConfig | null;
+  loading: boolean;
+  error: string | null;
+  refetch: () => Promise<void>;
+}
+
+// Create context
+const AppConfigContext = createContext<AppConfigContextValue | undefined>(undefined);
+
+/**
+ * Provider component that fetches and provides app configuration
+ * Should be placed at the top level of the app, before any components that need config
+ */
+export const AppConfigProvider: React.FC<{ children: React.ReactNode }> = ({ children }) => {
+  const [config, setConfig] = useState<AppConfig | null>(null);
+  const [loading, setLoading] = useState(true);
+  const [error, setError] = useState<string | null>(null);
+  const headers = useRequestHeaders();
+
+  const fetchConfig = async () => {
+    try {
+      setLoading(true);
+      setError(null);
+
+      const response = await fetch('/api/v1/config/app-config', {
+        headers,
+      });
+
+      if (!response.ok) {
+        throw new Error(`Failed to fetch config: ${response.status} ${response.statusText}`);
+      }
+
+      const data: AppConfig = await response.json();
+      setConfig(data);
+    } catch (err) {
+      const errorMessage = err instanceof Error ? err.message : 'Unknown error occurred';
+      setError(errorMessage);
+      console.error('[AppConfig] Failed to fetch app config:', err);
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  useEffect(() => {
+    fetchConfig();
+  }, []);
+
+  const value: AppConfigContextValue = {
+    config,
+    loading,
+    error,
+    refetch: fetchConfig,
+  };
+
+  return (
+    <AppConfigContext.Provider value={value}>
+      {children}
+    </AppConfigContext.Provider>
+  );
+};
+
+/**
+ * Hook to access application configuration
+ * Must be used within AppConfigProvider
+ */
+export function useAppConfig(): AppConfigContextValue {
+  const context = useContext(AppConfigContext);
+
+  if (context === undefined) {
+    throw new Error('useAppConfig must be used within AppConfigProvider');
+  }
+
+  return context;
+}
+