Infra audit: finish Go dependency remediation

[luke-lombardi]

Summary

• update golang.org/x/net to v0.55.0
• update github.com/redis/go-redis/v9 to v9.5.5
• update AWS S3/eventstream dependencies to remediated releases
• make the Redis configuration test fixture deterministic so it cannot generate an empty address list

Validation

• go mod verify
• go test -count=1 ./...
• git diff --check

[github-actions]

Benchmark Results

goos: linux
goarch: amd64
pkg: github.com/beam-cloud/blobcache-v2/pkg
cpu: AMD EPYC 7763 64-Core Processor                
BenchmarkBufferPool/size_1MB/WithPool-4         	49186618	        50.07 ns/op	      27 B/op	       1 allocs/op
BenchmarkBufferPool/size_1MB/WithoutPool-4      	    8160	    287023 ns/op	 1048576 B/op	       1 allocs/op
BenchmarkBufferPool/size_4MB/WithPool-4         	49279698	        48.04 ns/op	      31 B/op	       1 allocs/op
BenchmarkBufferPool/size_4MB/WithoutPool-4      	    3945	    604205 ns/op	 4194305 B/op	       1 allocs/op
BenchmarkBufferPool/size_16MB/WithPool-4        	50880121	        46.90 ns/op	      31 B/op	       1 allocs/op
BenchmarkBufferPool/size_16MB/WithoutPool-4     	    2347	    975524 ns/op	16777217 B/op	       1 allocs/op
PASS
ok  	github.com/beam-cloud/blobcache-v2/pkg	14.614s
{"level":"info","time":"2026-07-29T14:10:13Z","message":"Disk cache directory located at: '/tmp/BenchmarkGetContentDiskCache3292391114/001'"}
{"level":"info","time":"2026-07-29T14:10:13Z","message":"Memory cache DISABLED (disk-only mode)"}
{"level":"info","time":"2026-07-29T14:10:13Z","message":"Evicted object: test"}
goos: linux
goarch: amd64
pkg: github.com/beam-cloud/blobcache-v2/pkg
cpu: AMD EPYC 7763 64-Core Processor                
BenchmarkGetContentDiskCache-4   	{"level":"info","time":"2026-07-29T14:10:13Z","message":"Disk cache directory located at: '/tmp/BenchmarkGetContentDiskCache223366554/002'"}
{"level":"info","time":"2026-07-29T14:10:13Z","message":"Memory cache DISABLED (disk-only mode)"}
{"level":"info","time":"2026-07-29T14:10:14Z","message":"Evicted object: test"}
{"level":"info","time":"2026-07-29T14:10:14Z","message":"Disk cache directory located at: '/tmp/BenchmarkGetContentDiskCache718425711/003'"}
{"level":"info","time":"2026-07-29T14:10:14Z","message":"Memory cache DISABLED (disk-only mode)"}
{"level":"info","time":"2026-07-29T14:10:14Z","message":"Evicted object: test"}
     151	   3955775 ns/op	4241.20 MB/s	17440723 B/op	    1125 allocs/op
PASS
ok  	github.com/beam-cloud/blobcache-v2/pkg	1.112s