Move report_runner app under backend/report_runner

[pashiav]

Fixes #6763

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

Summary of Changes:

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

This is the 11th 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 Reorganize interactions app under backend/interactions/ #6756.

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 pr to documentation list
• Add automated tests
• Add a reverse migration if a migration is present in the PR

Testing instructions

Please cross check the following functionalities with main.

• Create a record that generates a report/invoice on save (e.g. Loan or Gift)
• Verify the report opens in a new tab

• Click Reports in the navigation bar
• Run a valid report
• Verify the report opens in a new tab

[emenslin]

Testing instructions

• Verify the report opens in a new tab
• Verify the report opens in a new tab

Looks good!

[bhumikaguptaa]

• Verify the report opens in a new tab
• Verify the report opens in a new tab

Works as expected!