feat: Implement blog and blog post models, routes, and services

- Added Blog and BlogPost models with necessary fields and relationships.
- Created blogRouter for handling blog-related API endpoints including CRUD operations.
- Developed BlogService for business logic related to blogs and posts, including sharing functionality.
- Implemented API client methods for frontend to interact with blog-related endpoints.
- Added internationalization support for blog-related text in English and German.
- Created Vue components for blog editing, listing, and viewing, including a rich text editor for post content.
- Enhanced user experience with form validations and dynamic visibility settings based on user input.

backend/controllers/navigationController.js

@@ -32,6 +32,10 @@ const menuStructure = {
                 visible: ["all"],
                 path: "/socialnetwork/guestbook"
             },
+            blog: {
+                visible: ["all"],
+                path: "/blogs"
+            },
             usersearch: {
                 visible: ["all"],
                 path: "/socialnetwork/search"