Use golangci-lint fmt to format code (#163)

Use `golangci-lint fmt` to format code, upgrading `.golangci.yml` to v2 and mirroring the linter configuration used by https://github.com/go-gitea/gitea. `gci` now handles import ordering into standard, project-local, blank, and default groups.

Mirrors https://github.com/go-gitea/gitea/pull/37194.

Changes:
- Upgrade `.golangci.yml` to v2 format with the same linter set as gitea (minus `prealloc`, `unparam`, `testifylint`, `nilnil` which produced too many pre-existing issues)
- Add path-based exclusions (`bodyclose`, `gosec` in tests; `gosec:G115`/`G117` globally)
- Run lint via `make lint-go` in CI instead of `golangci/golangci-lint-action`, matching the pattern used by other Gitea repos
- Apply safe auto-fixes (`modernize`, `perfsprint`, `usetesting`, etc.)
- Add explanations to existing `//nolint` directives
- Remove dead code (unused `newRemoteReusableWorkflow` and `networkName`), duplicate imports, and shadowed `max` builtins
- Replace deprecated `docker/distribution/reference` with `distribution/reference`
- Fix `Deprecated:` comment casing and simplify nil/len checks

---
This PR was written with the help of Claude Opus 4.7

Reviewed-on: https://gitea.com/gitea/act/pulls/163
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-committed-by: silverwind <me@silverwind.io>

pkg/common/draw.go

@@ -72,6 +72,7 @@ func (p *Pen) drawTopBars(buf io.Writer, labels ...string) {
 	}
 	fmt.Fprintf(buf, "\n")
 }
+
 func (p *Pen) drawBottomBars(buf io.Writer, labels ...string) {
 	style := styleDefs[p.style]
 	for _, label := range labels {
@@ -83,6 +84,7 @@ func (p *Pen) drawBottomBars(buf io.Writer, labels ...string) {
 	}
 	fmt.Fprintf(buf, "\n")
 }
+
 func (p *Pen) drawLabels(buf io.Writer, labels ...string) {
 	style := styleDefs[p.style]
 	for _, label := range labels {
@@ -125,11 +127,8 @@ func (p *Pen) DrawBoxes(labels ...string) *Drawing {
 
 // Draw to writer
 func (d *Drawing) Draw(writer io.Writer, centerOnWidth int) {
-	padSize := (centerOnWidth - d.GetWidth()) / 2
-	if padSize < 0 {
-		padSize = 0
-	}
-	for _, l := range strings.Split(d.buf.String(), "\n") {
+	padSize := max((centerOnWidth-d.GetWidth())/2, 0)
+	for l := range strings.SplitSeq(d.buf.String(), "\n") {
 		if len(l) > 0 {
 			padding := strings.Repeat(" ", padSize)
 			fmt.Fprintf(writer, "%s%s\n", padding, l)