Standardize BIP/BOLT reference format

[andrei-21]

Problem

The guide is inconsistent when it labels Bitcoin Improvement Proposals and Lightning BOLTs:

• BIP-353 (with hyphen)
• BIP 21 (with space)
• BOLT12 (no space)

Proposal

Adopt the single, space-separated form already used by the RFC series: "BIP 21", "BOLT 12", etc.

Let me know if you agree and I will proceed with a PR.