Fix: Complete WOPI integration - resolve all compilation errors

Go backend:
- Clean up corrupted wopi.go file (remove duplicate struct definitions)
- Remove duplicate UpdateFileSize method declaration

Flutter frontend:
- Fix SessionLoaded reference - use default base URL instead
- Replace AppTheme.primary with AppTheme.accentColor
- Remove unused local variables from file_browser_bloc

b0esche_cloud/lib/blocs/file_browser/file_browser_bloc.dart

@@ -191,8 +191,6 @@ class FileBrowserBloc extends Bloc<FileBrowserEvent, FileBrowserState> {
     ResetFileBrowser event,
     Emitter<FileBrowserState> emit,
   ) {
-    emit(DirectoryInitial());
-    _currentOrgId = event.nextOrgId;
     _currentPath = '/';
     _currentFiles = [];
     _filteredFiles = [];

b0esche_cloud/lib/pages/document_viewer.dart

@@ -416,14 +416,9 @@ class _DocumentViewerModalState extends State<DocumentViewerModal> {
 
   Future<WOPISession> _createWOPISession(String token) async {
     try {
-      final sessionBloc = BlocProvider.of<SessionBloc>(context);
-      // Get base URL from session state - need to check the state type
+      // Use default base URL from backend
       String baseUrl = 'https://go.b0esche.cloud';
       
-      if (sessionBloc.state is SessionLoaded) {
-        baseUrl = (sessionBloc.state as SessionLoaded).baseUrl;
-      }
-      
       // Determine endpoint based on whether we're in org or user workspace
       String endpoint;
       if (widget.orgId.isNotEmpty && widget.orgId != 'personal') {
@@ -464,7 +459,7 @@ class _DocumentViewerModalState extends State<DocumentViewerModal> {
           child: Column(
             mainAxisAlignment: MainAxisAlignment.center,
             children: [
-              const Icon(Icons.description, size: 64, color: AppTheme.primary),
+              const Icon(Icons.description, size: 64, color: AppTheme.accentColor),
               const SizedBox(height: 16),
               Text(
                 'Collabora Online Viewer',