Add branch protection rules to require CI checks to pass before merging

[MBanucu]

Problem

Currently, there are no branch protection rules on the repository. This allows PRs to be merged even when CI checks fail, as demonstrated by PR #9238, which had failing nix-desktop builds but was still merged. This can lead to broken builds being deployed.

Proposed Solution

Add branch protection rules for the dev branch (and others as needed) to require the following CI checks to pass:

• nix-desktop (builds the Nix flake on multiple platforms)
• test
• typecheck
• Any other critical checks

Benefits

• Ensures code quality and prevents merging broken changes.
• Catches issues like the Bun version mismatch early.
• Follows best practices for CI/CD.

Related Issues/PRs

• PR test(app): e2e tests #9238: Merged with failed nix-desktop checks.
• Issue Build failure: Bun version mismatch (expects 1.3.5, system has 1.3.6) #9583: Bun version issue that could have been caught.

This would prevent future issues and improve the reliability of the codebase.