Regenerate and rewrite init migration

[ostepan8]

ℹ️ Issue

Closes <#165>

📝 Description

Write a short summary of what you added. Why is it important? Any member of C4C should be able to read this and understand your contribution -- not just your team members.

updated the init migration so it only defines database enum types (no tables). the enum values were out of sync with our codebase and some enums were unused.

Briefly list the changes made to the code:

1. removed all table creation from the init migration. tables will be handled in separate migrations.
2. removed old/unused enums (commit_length_enum, site_enum, app_status_enum, school_enum, experience_type_enum, interest_area_enum, learner_info_school_enum).
3. kept only enums that our entities use: application_discipline_enum, admins_discipline_enum, discipline_name_enum, application_appstatus_enum, application_experiencetype_enum, application_interest_enum, application_applicanttype_enum, application_school_enum.
4. updated enum values to match our typescript enums (e.g. appstatus now has no availability, declined, active, inactive instead of rejected).
5. updated the down method to drop all created types with drop type if exists.

✔️ Verification

What steps did you take to verify your changes work? These should be clear enough for someone to be able to clone the branch and follow the steps themselves.

Provide screenshots of any new components, styling changes, or pages.

🏕️ (Optional) Future Work / Notes

Did you notice anything ugly during the course of this ticket? Any bugs, design challenges, or unexpected behavior? Write it down so we can clean it up in a future ticket!