Add vector compression and SVS-VAMANA tuning guide to docs

[tylerhutcherson]

Summary

Create a focused documentation guide for vector compression and SVS-VAMANA tuning in RedisVL.

Level: Intermediate

Current State

• Compression concepts are present but spread across notebooks and API docs.
• There is no single practical guide for when/how to use compression options and how to evaluate tradeoffs.

Proposed Change

• Add a docs guide (for example docs/user_guide/how_to_guides/vector_compression_tuning.md) that covers:
  • when compression is appropriate
  • choosing algorithm and key params
  • expected memory/latency/recall tradeoffs
  • safe rollout/testing checklist
  • links to relevant API docs and notebooks
• Include a minimal reproducible benchmark workflow users can run locally.

Definition of Done

• New guide is linked from docs navigation and related pages.
• Includes actionable tuning recommendations and validation checklist.
• make docs-build passes.

Out of Scope

• Changing compression implementation behavior in code.