Switch Redis catalog icon to the official Red wordmark SVG

The page previously used the Redis org GitHub avatar PNG (460x460,
cube mark). Swap to `Redis_Logo_Red_RGB.svg` from the official Redis
brand kit (sourced via redis/redis-vl-python), matching the logo used
in the adk-redis README hero. SVG is acceptable for catalog assets
(see goodmem.svg precedent).

Note: this asset is a wordmark (viewBox ~500x156), wider than peer
catalog cards which are mostly square. If it renders awkwardly on the
catalog grid, swap back to a square cube-mark variant.

- Add `docs/integrations/assets/redis.svg`.
- Update `catalog_icon` in `redis.md` frontmatter.
- Drop `docs/integrations/assets/redis.png`.

Verified with `mkdocs build --strict`.

Author: nkanu17

docs/integrations/assets/redis.png

@@ -1,7 +1,7 @@
 ---
 catalog_title: Redis
 catalog_description: Vector, hybrid, and SQL search plus session, memory, and semantic cache for agents
-catalog_icon: /integrations/assets/redis.png
+catalog_icon: /integrations/assets/redis.svg
 catalog_tags: ["data","mcp"]
 ---