Update Wazuh agent documentation for 5.0

[javimed]

Description

This PR updates the Wazuh agent documentation for Wazuh 5.0: it adds enrollment token, password, and CA configuration steps, publishes the deployment variables section, corrects dashboard menu paths, and refreshes the troubleshooting, connection, removal, and upgrade pages, including the new Upgrading the Wazuh agent page.

🤖 Drafted by Claude

Documentation compilation

• Verify that documentation compiles without warnings.

Changelog

• Update CHANGELOG.md.

Web optimization & code formatting

• Page references
  • Update /_static/js/redirects.js if necessary (guide).
  • Update /llms.txt if necessary.
• Add or update meta descriptions.
• Use three-space indentation in .rst files.

Writing style

• Use bold for UI elements, italics for key terms and emphasis, and code font for Bash commands, file names, REST paths, and code.
• Follow present tense, active voice, and a semi-formal tone.
• Write short, clear, and concise sentences.

🤖 Generated with Claude Code