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/runner.go

@@ -7,6 +7,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"maps"
 	"path/filepath"
 	"strings"
 	"sync"
@@ -49,9 +50,7 @@ func NewRunner(cfg *config.Config, reg *config.Registration, cli client.Client)
 		}
 	}
 	envs := make(map[string]string, len(cfg.Runner.Envs))
-	for k, v := range cfg.Runner.Envs {
-		envs[k] = v
-	}
+	maps.Copy(envs, cfg.Runner.Envs)
 	if cfg.Cache.Enabled == nil || *cfg.Cache.Enabled {
 		if cfg.Cache.ExternalServer != "" {
 			envs["ACTIONS_CACHE_URL"] = cfg.Cache.ExternalServer
@@ -116,7 +115,7 @@ func (r *Runner) Run(ctx context.Context, task *runnerv1.Task) error {
 // getDefaultActionsURL
 // when DEFAULT_ACTIONS_URL == "https://github.com" and GithubMirror is not blank,
 // it should be set to GithubMirror first.
-func (r *Runner) getDefaultActionsURL(ctx context.Context, task *runnerv1.Task) string {
+func (r *Runner) getDefaultActionsURL(task *runnerv1.Task) string {
 	giteaDefaultActionsURL := task.Context.Fields["gitea_default_actions_url"].GetStringValue()
 	if giteaDefaultActionsURL == "https://github.com" && r.cfg.Runner.GithubMirror != "" {
 		return r.cfg.Runner.GithubMirror
@@ -148,7 +147,7 @@ func (r *Runner) run(ctx context.Context, task *runnerv1.Task, reporter *report.
 	taskContext := task.Context.Fields
 
 	log.Infof("task %v repo is %v %v %v", task.Id, taskContext["repository"].GetStringValue(),
-		r.getDefaultActionsURL(ctx, task),
+		r.getDefaultActionsURL(task),
 		r.client.Address())
 
 	preset := &model.GithubContext{
@@ -174,8 +173,8 @@ func (r *Runner) run(ctx context.Context, task *runnerv1.Task, reporter *report.
 		preset.Token = t
 	}
 
-	if actionsIdTokenRequestUrl := taskContext["actions_id_token_request_url"].GetStringValue(); actionsIdTokenRequestUrl != "" {
-		r.envs["ACTIONS_ID_TOKEN_REQUEST_URL"] = actionsIdTokenRequestUrl
+	if actionsIDTokenRequestURL := taskContext["actions_id_token_request_url"].GetStringValue(); actionsIDTokenRequestURL != "" {
+		r.envs["ACTIONS_ID_TOKEN_REQUEST_URL"] = actionsIDTokenRequestURL
 		r.envs["ACTIONS_ID_TOKEN_REQUEST_TOKEN"] = taskContext["actions_id_token_request_token"].GetStringValue()
 		task.Secrets["ACTIONS_ID_TOKEN_REQUEST_TOKEN"] = r.envs["ACTIONS_ID_TOKEN_REQUEST_TOKEN"]
 	}
@@ -222,7 +221,7 @@ func (r *Runner) run(ctx context.Context, task *runnerv1.Task, reporter *report.
 		ContainerOptions:      r.cfg.Container.Options,
 		ContainerDaemonSocket: r.cfg.Container.DockerHost,
 		Privileged:            r.cfg.Container.Privileged,
-		DefaultActionInstance: r.getDefaultActionsURL(ctx, task),
+		DefaultActionInstance: r.getDefaultActionsURL(task),
 		PlatformPicker:        r.labels.PickPlatform,
 		Vars:                  task.Vars,
 		ValidVolumes:          r.cfg.Container.ValidVolumes,