Add back-end & administration pages

[supercodestart]

Add back-end & administration pages

• add interfaces, models, repositories, and services for PostgreSQL management. #90
• add user management #92
• add automation for table migrations
• add middleware for authentication via JWT #127
• add login page
• add reCAPTCHA v2
• add security page
• add audits page
• add profile management #123
• add experience management #125
• add skill management
• add link management
• add text management via markdown
• add SEO meta management