Normalize CHANGELOG.md structure

[nanotaboada]

Problem

CHANGELOG.md has two structural issues that need to be fixed for consistency across all repos.

Proposed Solution

Apply the following changes to CHANGELOG.md:

1. Remove the ## How to Release section (the full block including the pre-release checklist and step-by-step instructions) — this content belongs in RELEASES.md, not in the changelog. Keep the <!-- Template for new releases: --> comment that follows it.

2. Capitalize release codenames in ## version headers and in the matching reference links at the bottom:

   • [1.0.0 - azteca] → [1.0.0 - Azteca]
   • [1.1.0 - bernabeu] → [1.1.0 - Bernabeu]
   • [2.0.0 - centenario] → [2.0.0 - Centenario]
   • [2.1.0 - dusseldorf] → [2.1.0 - Dusseldorf]
   • [2.1.1 - ekaterinburg] → [2.1.1 - Ekaterinburg]

Acceptance Criteria

• ## How to Release section removed; template comment kept
• All five codenames capitalized in ## headers
• All five codenames capitalized in reference links at the bottom
• No other content changed

[coderabbitai]

🔗 Related PRs

#217 - chore: add project structure diagram [merged]
#422 - chore(changelog): prepare CHANGELOG for 2.0.0 - centenario [merged]
#438 - docs: prepare changelog for v2.1.0-dusseldorf release [merged]
#446 - chore(claude): rename and extend slash commands [merged]
#449 - docs: normalize README structure and add RELEASES.md [merged]
#467 - docs(changelog): prepare release notes for v2.1.1-ekaterinburg [merged]

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