Add content for Git bundling

[braboj]

As a reader working in constrained environments, I want to understand Git bundles so that I can transfer repository data without network access.

What

Add content covering git bundle — creating, verifying, and applying bundles for offline repository transfer.

Why

Git bundling is useful in air-gapped environments, sneakernet transfers, and as a lightweight backup mechanism. It's a niche but practical feature that complements the remote operations chapter.

Acceptance criteria

• Explain what a bundle is (single-file repo snapshot)
• Show how to create a bundle (git bundle create)
• Show how to verify and clone/pull from a bundle
• Use case examples (air-gapped transfer, email-based collaboration)
• Comparison with git archive (bundles include history, archives don't)