fix(docker): correct builder tag to golang:1.26.5-alpine3.24 (unbreak main)

[szibis]

Urgent — fixes broken main

#472 bumped the builder to golang:1.26.5-alpine3.22, which does not exist on Docker Hub (Alpine moved to 3.23/3.24 for the 1.26.5 line). The docker build and every downstream e2e job now fail on main:

ERROR: docker.io/library/golang:1.26.5-alpine3.22: not found

Fix

Pin to golang:1.26.5-alpine3.24 (newest Alpine for this Go line).

Verification

docker build . → succeeds, produces both loki-vl-proxy and healthcheck binaries. ✅

[github-actions]

PR Quality Report

Compared against base branch main.

Coverage and tests

Signal	Base	PR	Delta
Test count	4792	4792	0
Coverage	85.1%	85.1%	0.0% (stable)

Compatibility

Track	Base	PR	Delta
Loki API	100.0%	11/11 (100.0%)	0.0% (stable)
Logs Drilldown	100.0%	17/17 (100.0%)	0.0% (stable)
VictoriaLogs	100.0%	11/11 (100.0%)	0.0% (stable)

Performance smoke

Lower CPU cost (ns/op) is better. Lower benchmark memory cost (B/op, allocs/op) is better. Higher throughput is better. Lower load-test memory growth is better. Benchmark rows are medians from repeated samples.

Signal	Base	PR	Delta
QueryRange cache-hit CPU cost	3030.0 ns/op	3110.0 ns/op	+2.6% (stable)
QueryRange cache-hit memory	1184.0 B/op	1184.0 B/op	0.0% (stable)
QueryRange cache-hit allocations	29.0 allocs/op	29.0 allocs/op	0.0% (stable)
QueryRange cache-bypass CPU cost	3370.0 ns/op	3262.0 ns/op	-3.2% (stable)
QueryRange cache-bypass memory	1245.0 B/op	1245.0 B/op	0.0% (stable)
QueryRange cache-bypass allocations	30.0 allocs/op	30.0 allocs/op	0.0% (stable)
Labels cache-hit CPU cost	687.2 ns/op	719.4 ns/op	+4.7% (stable)
Labels cache-hit memory	48.0 B/op	48.0 B/op	0.0% (stable)
Labels cache-hit allocations	3.0 allocs/op	3.0 allocs/op	0.0% (stable)
Labels cache-bypass CPU cost	1261.0 ns/op	1277.0 ns/op	+1.3% (stable)
Labels cache-bypass memory	391.0 B/op	391.0 B/op	0.0% (stable)
Labels cache-bypass allocations	14.0 allocs/op	14.0 allocs/op	0.0% (stable)

State

• Coverage, compatibility, and sampled performance are reported here from the same PR workflow.
• This is a delta report, not a release gate by itself. Required checks still decide merge safety.
• Performance is a smoke comparison, not a full benchmark lab run.
• Delta states use the same noise guards as the quality gate (percent + absolute + low-baseline checks), so report labels match merge-gate behavior.