fix CGO-related Docker build issues

[peterldowns]

I'm seeing cgo-related errors on the main branch:

https://github.com/peterldowns/pgmigrate/actions/runs/13402236158/job/37435471414

#41 [linux/arm64 builder 13/13] RUN go build   -ldflags "-X github.com/peterldowns/pgmigrate/cmd/pgmigrate/shared.Version=v0.2.0 -X github.com/peterldowns/pgmigrate/cmd/pgmigrate/shared.Commit=639e8e5"   -o /dist/pgmigrate   ./cmd/pgmigrate
#41 35.55 # runtime/cgo
#41 35.55 gcc: error: unrecognized command-line option '-fno-caret-diagnostics'
#41 ERROR: process "/dev/.buildkit_qemu_emulator /bin/sh -c go build   -ldflags \"-X github.com/peterldowns/pgmigrate/cmd/pgmigrate/shared.Version=${PGM_VERSION} -X github.com/peterldowns/pgmigrate/cmd/pgmigrate/shared.Commit=${PGM_COMMIT_SHA}\"   -o /dist/pgmigrate   ./cmd/pgmigrate" did not complete successfully: exit code: 1
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 > [linux/arm64 builder 13/13] RUN go build   -ldflags "-X github.com/peterldowns/pgmigrate/cmd/pgmigrate/shared.Version=v0.2.0 -X github.com/peterldowns/pgmigrate/cmd/pgmigrate/shared.Commit=639e8e5"   -o /dist/pgmigrate   ./cmd/pgmigrate:
35.55 # runtime/cgo
35.55 gcc: error: unrecognized command-line option '-fno-caret-diagnostics'
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This is absolutely terrible. I have no idea why gcc is failing. But, here's how I'm trying to fix it:

• Update the development shell and the nix build to use go1.24
  • also update golangci-lint in CI to match the version used in development
  • we have to update it in CI for it to be able to work with code built with go1.24, anyway
• Update CI to use go1.24, both for the golang workflows and the docker workflows
• Update the Dockerfile to use go1.24 and alpine 3.21
• Update the Dockerfile to set CGO_ENABLED=0
  • I don't know why it was set to CGO_ENABLED=1
  • The local development shell sets CGO_ENABLED=0 and pgmigrate still seems to work fine
  • The release binaries are built with CGO_ENABLED=0, and those are what people are brew installing, and everything seems to work fine.

I tested this change by running just docker-build and then running docker run --rm -it local-pgmigrate:latest pgmigrate version and it seemed to work correctly, so hopefully everything is cool.