docs: rewrite README for presentation readiness (#408)

* docs: rewrite README for presentation readiness

- Add hero section with clear value proposition
- Create 'Why redisctl?' section explaining benefits over raw APIs
- Add feature showcase with before/after examples
- Include 4 real-world usage scenarios
- Move installation section lower after establishing value
- Streamline quick start to 3 simple steps
- Maintain all technical accuracy while improving readability

* docs: remove emojis from README

Author: joshrotenberg