chore(deps): bump redis from 7.4.1 to 8.1.0 in /backend

Bumps [redis](https://github.com/redis/redis-py) from 7.4.1 to 8.1.0.
- [Release notes](https://github.com/redis/redis-py/releases)
- [Changelog](https://github.com/redis/redis-py/blob/master/CHANGES)
- [Commits](redis/redis-py@v7.4.1...v8.1.0)

---
updated-dependencies:
- dependency-name: redis
  dependency-version: 8.1.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

backend/pyproject.toml

@@ -49,7 +49,7 @@ dependencies = [
     "python-dotenv>=1.2.2,<2",
     "pyjwt[crypto]>=2.12,<3",
     "python-multipart>=0.0.31,<1",
-    "redis[hiredis]>=7.1,<8",
+    "redis[hiredis]>=7.1,<9",
     "scikit-learn>=1.8,<2",
     "sqlalchemy>=2.0.46,<2.1",
     "sqlalchemy-crud-plus>=1.3,<2",

backend/requirements.txt

@@ -269,7 +269,7 @@ pyyaml==6.0.3
     # via
     #   langchain-core
     #   uvicorn
-redis==7.4.1
+redis==8.1.0
     # via unigraph-backend (backend/pyproject.toml)
 regex==2026.7.19
     # via tiktoken