Move permissions app under backend/permissions/

[pashiav]

Fixes #6615

This PR reorganizes the project structure by moving the permissions app into a new backend/permissions/ directory under specifyweb/.

Summary of Changes:

• Moved permissions to specifyweb/backend/permissions/
• Updated all import paths to reflect the new location
• Updated SPECIFY_APPS in settings.py to include specifyweb.backend.permissions

This is the 2nd PR in a broader backend reorganization. No frontend behavior or functionality was changed.

Notes:

• This PR requires a rebuild for the changes to take effect properly.
• This PR is built on Move accounts app under backend/accounts/ #6577.

Checklist

• Self-review the PR after opening it to make sure the changes look good and
  self-explanatory (or properly documented)
• Add relevant issue to release milestone
• Add relevant documentation (Tester - Dev)
• Add automated tests
• Add a reverse migration if a migration is present in the PR

Testing instructions

See more info on Permissions

Please cross check the following functionalities with main.

• General Permissions testing
  Verify that you can:
  • Create new Role from Library
  • Create new Role from existing Role
  • Create completely new Role
  • Import Roles
  • Export Roles
  • Edit Name/Description fields on User Roles
  • Delete a Role
  • Create a role that grants edit access and assign it to a user
  • Apply custom collection-level policies to a user
  • Test the policies and roles you apply to a user
  • Verify permissions are still enforced correctly in Workbench
    • Validate & Upload a valid dataset
  • Verify permissions are still enforced correctly in Queries

[bhumikaguptaa]

• General Permissions testing
  Verify that you can:
  • Create new Role from Library
  • Create new Role from existing Role
  • Create completely new Role
  • Import Roles
  • Export Roles
  • Edit Name/Description fields on User Roles
  • Delete a Role
  • Create a role that grants edit access and assign it to a user
  • Apply custom collection-level policies to a user
  • Test the policies and roles you apply to a user
  • Verify permissions are still enforced correctly in Workbench
    • Validate & Upload a valid dataset
  • Verify permissions are still enforced correctly in Queries

Works as expected!

[emenslin]

Testing instructions

• General Permissions testing
  • Create new Role from Library
  • Create new Role from existing Role
  • Create completely new Role
  • Import Roles
  • Export Roles
  • Edit Name/Description fields on User Roles
  • Delete a Role
  • Create a role that grants edit access and assign it to a user
  • Apply custom collection-level policies to a user
  • Test the policies and roles you apply to a user
  • Verify permissions are still enforced correctly in Workbench
    • Validate & Upload a valid dataset
  • Verify permissions are still enforced correctly in Queries

Looks good!