ci: fix make build error

We only want to use the GOTOOLCHAIN if it's set otherwise fallback to
the go.mod toolchain version.

Error message:

    docker: invalid reference format.
    See 'docker run --help'.
    make: *** [Makefile:128: build-linux-arm-7] Error 125

See https://github.com/gotify/server/actions/runs/14690165536/job/41224267750

chore(deps): update golangci/golangci-lint-action action to v7 (#787)

* chore(deps): update golangci/golangci-lint-action action to v7

* bump golangci-lint version

Signed-off-by: eternal-flame-AD <yume@yumechi.jp>

---------

Signed-off-by: eternal-flame-AD <yume@yumechi.jp>
Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: eternal-flame-AD <yume@yumechi.jp>

Merge pull request #734 from gotify/panic-bool

fix: panic when setting bool via envvar

Merge pull request #733 from gotify/silent

fix: enable silent mode

Merge pull request #661 from gotify/update-backend

Update backend dependencies

Merge pull request #592 from gotify/build

Build

Add default message priority for applications


Co-authored-by: Jannis Mattheis <contact@jmattheis.de>

Add delete application image endpoint

Fix swagger-ui style

Unify display of app icon