chore(lint): add golangci-lint v2 and fix all lint issues (#803)

## Summary
- Replace old `.golangci.yml` (v1 format) with v2 format, aligned with gitea's lint config
- Add `lint-go`, `lint-go-fix`, and `lint` Makefile targets using golangci-lint v2.10.1
- Replace `make vet` with `make lint` in CI workflow (lint includes vet)
- Fix all 35 lint issues: modernize (maps.Copy, range over int, any), perfsprint (errors.New), unparam (remove unused parameters), revive (var naming), staticcheck, forbidigo exclusion for cmd/
- Make `security-check` non-fatal (apply https://github.com/go-gitea/gitea/pull/36681)
- Remove dead gocritic exclusion rules (commentFormatting, exitAfterDefer)
- Remove dead linter exclusions and disabled checks (singleCaseSwitch, ST1003, QF1001, QF1006, QF1008, testifylint go-require/require-error, test file exclusions for dupl/errcheck/staticcheck/unparam)

## Test plan
- [x] `golangci-lint run` passes
- [x] `go build ./...` passes
- [x] `go test ./...` passes

---------

Co-authored-by: ChristopherHX <christopher.homberger@web.de>
Co-authored-by: Christopher Homberger <christopher.homberger@web.de>
Reviewed-on: https://gitea.com/gitea/act_runner/pulls/803
Reviewed-by: ChristopherHX <christopherhx@noreply.gitea.com>

internal/app/run/workflow_test.go

@@ -307,7 +307,7 @@ func Test_yamlV4NodeRoundTrip(t *testing.T) {
 	t.Run("unmarshal and re-marshal workflow", func(t *testing.T) {
 		input := []byte("name: test\non: push\njobs:\n    build:\n        runs-on: ubuntu-latest\n        steps:\n            - run: echo hello\n")
 
-		var wf map[string]interface{}
+		var wf map[string]any
 		err := yaml.Unmarshal(input, &wf)
 		require.NoError(t, err)
 		assert.Equal(t, wf["name"], "test")
@@ -315,7 +315,7 @@ func Test_yamlV4NodeRoundTrip(t *testing.T) {
 		out, err := yaml.Marshal(wf)
 		require.NoError(t, err)
 
-		var wf2 map[string]interface{}
+		var wf2 map[string]any
 		err = yaml.Unmarshal(out, &wf2)
 		require.NoError(t, err)
 		assert.Equal(t, wf2["name"], "test")