Pin Redis version in Makefile

[UdeshyaDhungana]

Note

Low Risk
Low risk: only changes the Linux make setup install steps by adding apt pinning for Redis, affecting local/CI environment setup but not application runtime code.

Overview
The Makefile’s setup target now pins the Redis apt package by writing an /etc/apt/preferences.d/redis-8.4.pref file that forces installation of Redis 6:8.4* with high priority before running apt-get install redis.

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