🚀 ci: push beta bump via deploy key to bypass develop ruleset

[andycreed0x]

Purpose

Fix the auto beta-bump CI job, which was failing to push its commit back to develop because the branch's required-checks ruleset rejects any push whose commit never had a passing "Run tests" run — which the bump commit can never have.

Description

develop's branch protection was migrated from a classic rule to a ruleset (protect-develop) so that a bypass actor could be configured. GITHUB_TOKEN cannot be added as a bypass actor in this org (GitHub Actions app bypass requires an org owner to register the app at the org level, which we don't have). A repo deploy key can be added as a bypass actor, so the push-back now authenticates over SSH with a dedicated deploy key instead of GITHUB_TOKEN.

Main Changes

• 🔒️ Checkout now authenticates with secrets.DEVELOP_DEPLOY_KEY (a write-access deploy key registered as a bypass actor on the develop ruleset) instead of the default GITHUB_TOKEN, so the bump commit push isn't blocked by the required "Run tests" check
• 🔧 Dropped the job's permissions: contents: write to contents: read, since the token is no longer used for the push
• 📝 Updated inline comments to reflect that deploy-key pushes (unlike GITHUB_TOKEN pushes) do re-trigger workflows, so [skip ci] is now the only anti-loop guard

⚠️ Breaking Changes

• Requires the DEVELOP_DEPLOY_KEY repo secret to exist (already provisioned) and the corresponding deploy key to remain registered with write access on the repo
• develop branch protection is now enforced via a repository ruleset (protect-develop) instead of classic branch protection; equivalent rules (required "Run tests" check, no force-push, no deletion) with admin + deploy-key bypass

Checklist

• No hardcoded values (they should go in constants.py, .env, or our database)
• Added/updated tests (if necessary)
• Added/updated relevant documentation (if necessary)