Create "Why Not Just Use Jira?" Explanation

[patdhlk]

Description

Address the most common objection directly with a balanced explanation that acknowledges Jira's strengths while highlighting X-as-Code advantages.

Acceptance Criteria

• Create docs/faq/why-not-jira.rst or add to existing FAQ
• Address honestly:
  • When Jira IS the right choice
  • When X-as-Code is better
  • Hybrid approaches
• Key differentiators to highlight:
  • Version control for requirements
  • Review process (PRs for requirements)
  • Proximity to code
  • No vendor lock-in
  • Cost at scale
• Include Enterprise Tip about ubConnect for best-of-both-worlds