docs: add Jedis 4.x compatibility layer migration guide

[Aryex]

Summary

Adds documentation for the new Jedis 4.x Compatibility Layer, a drop-in replacement for Jedis 4.0.x–4.4.x applications migrating to Valkey GLIDE.

⚠️ Attention: This PR was generated automatically. Verify that all relevant pages have been updated.

Source Commits

• f7394d2 — feat(jedis-v4): add jedis-v4 migration layer (#5751)

Changes

• Added new documentation section: migration/java/jedis/jedis-4-compatibility-layer/
  • Overview page explaining why a separate 4.x layer exists and key differences from 5.x layer
  • Step-by-step migration guide with Gradle/Maven dependency examples and platform classifiers
  • Supported features page covering client types, commands, and limitations
  • Configuration mapping page showing how Jedis 4.x configs translate to GLIDE
• Updated migration/java/jedis/index.mdx to add a LinkCard for the Jedis 4.x layer
• Updated astro.config.mjs sidebar to include the new section

Context

The source commit adds a new Gradle module jedis-4-compatibility under java/ that provides Jedis 4.x API compatibility for Valkey GLIDE. This is separate from the existing jedis-compatibility module (targeting Jedis 5.x) because Jedis 5 introduced breaking type changes (JedisPooled generics, RESP3 APIs). Applications still on Jedis 4.x need this dedicated compatibility artifact.

cc @prashanna-frsh

---

This PR was generated by the automated documentation pipeline.

[jeremyprime]

The version in this file (2.1.0) is outdated. We should use a placeholder or pull from versions.ts. See other uses of versions throughout the docs to ensure consistent.