Gate deploy on CI checks and fix all checks

[AidanHT]

Workflows:

• deploy.yml now runs the full check suite (via checks.yml workflow_call) before build/deploy, so a red commit never ships -- including direct pushes to develop. Removed the duplicate main.yml and consolidated onto a single reusable checks.yml. PR checks use pull_request with a throwaway test SECRET_KEY instead of pull_request_target with the production key.

Formatting:

• Reformat 35 files with Black (24.1.0) and 2 JS files with Prettier.

Backend tests (were 120 failing, identical on develop):

• Realign stale shared/form fixtures to the current Application model (drop removed what_hackathon_experience, fix field names, add required fields).
• ApplicationForm.clean() uses .get() so a missing field is a validation error rather than a 500.
• Override the hardware sign-out window in date-dependent order tests and complete OrderSubmissionWithLockTestCase (team/user2/helper).
• Update hardware serializer/response expectations (credits, total_credits, packing_admin, hardware_name).
• Use the Submitted -> In Progress order status transition.
• Widen the phone-number validator to accept formatted numbers and reject overly long ones.
• Align accepted/waitlisted email tests to the current templates.

Overview

• Resolves #

Unit Tests Created

Steps to QA