Refactor image processing and add image file serving functionality

- Updated image directory handling to prioritize mounted volume for persistence.
- Enhanced logging for directory write tests and fallback mechanisms.
- Introduced a new endpoint to serve image files directly from local paths.
- Added error handling for file serving, including checks for file existence and readability.
- Updated the frontend to include a new ContentView component and corresponding route.

frontend/src/services/api.ts

@@ -1589,3 +1589,7 @@ export async function fetchContent(filters: ContentFilters = {}): Promise<Conten
   return fetchAPI(`/v1/writer/content/${queryString ? `?${queryString}` : ''}`);
 }
 
+export async function fetchContentById(id: number): Promise<Content> {
+  return fetchAPI(`/v1/writer/content/${id}/`);
+}
+