Improvements to Database Schema for Job Functionality

[AhmedMohamedAbdelaty]

We need to improve our current database schema to better support job-related functionalities.

Proposed Changes for the jobs table

1. Add experience_level, for example: 'Entry', 'Intermediate', 'Expert'.
2. Add estimated_duration.
3. Add a deadline for the job.
4. Support categories. We'll introduce categories for jobs. This will make it easier for freelancers to find work in their specific areas of expertise.

Proposed Changes for the proposals table

1. Add estimated_duration.
2. Support Attachments
3. Add updated_at column.