refactor(frontend): Remove '/api' prefix from all API calls to align with backend URL convention

- Updated all API endpoint strings in 'frontend/src' (via sed and manual fixes) to remove the '/api/' prefix.
- Manually fixed 'Timeline.tsx' absolute URLs to use the 'api' subdomain and correct path.
- Manually fixed 'useAuth.ts' logout fetch URLs.
- Updated 'HelpApiDocs.tsx' sandbox URL.
- This change, combined with the backend URL update, fully transitions the application to use subdomain-based routing (e.g., 'http://api.lvh.me:8000/resource/') instead of path-prefix routing (e.g., 'http://api.lvh.me:8000/api/resource/').

frontend/src/pages/PluginMarketplace.tsx

@@ -95,7 +95,7 @@ const PluginMarketplace: React.FC = () => {
   const { data: plugins = [], isLoading, error } = useQuery<PluginTemplate[]>({
     queryKey: ['plugin-templates', 'marketplace'],
     queryFn: async () => {
-      const { data } = await api.get('/api/plugin-templates/?view=marketplace');
+      const { data } = await api.get('/plugin-templates/?view=marketplace');
       return data.map((p: any) => ({
         id: String(p.id),
         name: p.name,
@@ -120,7 +120,7 @@ const PluginMarketplace: React.FC = () => {
   const { data: installedPlugins = [] } = useQuery<{ template: number }[]>({
     queryKey: ['plugin-installations'],
     queryFn: async () => {
-      const { data } = await api.get('/api/plugin-installations/');
+      const { data } = await api.get('/plugin-installations/');
       return data;
     },
   });
@@ -133,7 +133,7 @@ const PluginMarketplace: React.FC = () => {
   // Install plugin mutation
   const installMutation = useMutation({
     mutationFn: async (templateId: string) => {
-      const { data } = await api.post('/api/plugin-installations/', {
+      const { data } = await api.post('/plugin-installations/', {
         template: templateId,
       });
       return data;
@@ -187,7 +187,7 @@ const PluginMarketplace: React.FC = () => {
     // Fetch full plugin details including plugin_code
     setIsLoadingDetails(true);
     try {
-      const { data } = await api.get(`/api/plugin-templates/${plugin.id}/`);
+      const { data } = await api.get(`/plugin-templates/${plugin.id}/`);
       setSelectedPlugin({
         ...plugin,
         pluginCode: data.plugin_code,