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/models/community/blog.js

@@ -0,0 +1,60 @@
+import { Model, DataTypes } from 'sequelize';
+import { sequelize } from '../../utils/sequelize.js';
+
+class Blog extends Model {}
+
+Blog.init({
+  userId: {
+    type: DataTypes.INTEGER,
+    allowNull: false,
+    field: 'user_id'
+  },
+  title: {
+    type: DataTypes.STRING(255),
+    allowNull: false,
+  },
+  description: {
+    type: DataTypes.TEXT,
+    allowNull: true,
+  },
+  // 'public' or 'logged_in'
+  visibility: {
+    type: DataTypes.STRING(20),
+    allowNull: false,
+    defaultValue: 'public',
+  },
+  ageMin: {
+    type: DataTypes.INTEGER,
+    allowNull: true,
+    field: 'age_min'
+  },
+  ageMax: {
+    type: DataTypes.INTEGER,
+    allowNull: true,
+    field: 'age_max'
+  },
+  // 'm' | 'f' | null; comma-separated for future-proofing (e.g., 'm,f')
+  genders: {
+    type: DataTypes.STRING(10),
+    allowNull: true,
+  },
+  createdAt: {
+    type: DataTypes.DATE,
+    defaultValue: DataTypes.NOW,
+    field: 'created_at'
+  },
+  updatedAt: {
+    type: DataTypes.DATE,
+    defaultValue: DataTypes.NOW,
+    field: 'updated_at'
+  }
+}, {
+  sequelize,
+  modelName: 'Blog',
+  tableName: 'blog',
+  schema: 'community',
+  timestamps: true,
+  underscored: true,
+});
+
+export default Blog;