ci: update golangci-lint config and GitHub Action versions

[arran4]

Remove .golangci.yml configuration file as the repository uses default linting rules. Update actions/setup-go from v5 to v6 and golangci/golangci-lint-action from v6 to v9 in the CI workflow to support Go 1.25.0 and ensure correct linting environments.

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PR created automatically by Jules for task 11189437304072821718 started by @arran4

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[arran4]

@jules perfect now let's solve lint.

run golangci-lint
  Running [/home/runner/golangci-lint-2.11.4-linux-amd64/golangci-lint config path] in [/home/runner/work/gobookmarks/gobookmarks] ...
  Running [/home/runner/golangci-lint-2.11.4-linux-amd64/golangci-lint run] in [/home/runner/work/gobookmarks/gobookmarks] ...
  Error: cmd/gobookmarks/db_users_command.go:60:16: Error return value of `db.Close` is not checked (errcheck)
  	defer db.Close()
  	              ^
  Error: cmd/gobookmarks/help_command.go:43:19: Error return value of `(*flag.FlagSet).Parse` is not checked (errcheck)
  	c.FlagSet().Parse(args)
  	                 ^
  Error: cmd/gobookmarks/serve.go:455:22: Error return value of `certFile.Close` is not checked (errcheck)
  	defer certFile.Close()
  	                    ^
  Error: cmd/gobookmarks/serve.go:464:21: Error return value of `keyFile.Close` is not checked (errcheck)
  	defer keyFile.Close()
  	                   ^
  Error: cmd/gobookmarks/test_verification_template_command.go:306:11: Error return value of `w.Write` is not checked (errcheck)
  			w.Write(output)
  			       ^
  Error: config.go:283:15: Error return value of `f.Close` is not checked (errcheck)
  	defer f.Close()
  	             ^
  Error: config.go:298:13: Error return value of `os.Setenv` is not checked (errcheck)
  			os.Setenv(key, val)
  			         ^
  Error: db.go:23:11: Error return value of `db.Close` is not checked (errcheck)
  		db.Close()
  		        ^
  Error: db.go:28:11: Error return value of `db.Close` is not checked (errcheck)
  		db.Close()
  		        ^
  Error: favicon_proxy_test.go:15:10: Error return value of `w.Write` is not checked (errcheck)
  		w.Write([]byte("<link rel='icon' href='/favicon.ico'>"))
  		       ^
  Error: favicon_proxy_test.go:21:10: Error return value of `w.Write` is not checked (errcheck)
  		w.Write(icon)
  		       ^
  Error: provider_sql.go:68:18: Error return value of `rows.Close` is not checked (errcheck)
  	defer rows.Close()
  	                ^
  Error: provider_sql.go:91:18: Error return value of `rows.Close` is not checked (errcheck)
  	defer rows.Close()
  	                ^
  Error: provider_sql.go:123:18: Error return value of `rows.Close` is not checked (errcheck)
  	defer rows.Close()
  	                ^
  Error: provider_sql.go:229:14: Error return value of `tx.Rollback` is not checked (errcheck)
  		tx.Rollback()
  		           ^
  Error: provider_sql.go:233:14: Error return value of `tx.Rollback` is not checked (errcheck)
  		tx.Rollback()
  		           ^
  Error: provider_sql.go:244:14: Error return value of `tx.Rollback` is not checked (errcheck)
  		tx.Rollback()
  		           ^
  Error: funcs.go:224:8: ineffectual assignment to bookmark (ineffassign)
  			var bookmark = defaultBookmarks
  			    ^
  Error: funcs.go:253:8: ineffectual assignment to bookmark (ineffassign)
  			var bookmark = defaultBookmarks
  			    ^
  Error: funcs.go:293:8: ineffectual assignment to bookmark (ineffassign)
  			var bookmark = defaultBookmarks
  			    ^
  Error: authHandlers.go:32:7: QF1008: could remove embedded field "CoreData" from selector (staticcheck)
  	data.CoreData.UserRef = ""
  	     ^
  Error: bookmarkTabEdit.go:104:19: QF1001: could apply De Morgan's law (staticcheck)
  	includeHeader := !(idx == 0 && newName == "")
  	                 ^
  Error: bookmark_methods_test.go:122:11: ST1023: should omit type BookmarkList from declaration; it will be inferred from the right-hand side (staticcheck)
  	var list BookmarkList = tabs
  	         ^
  Error: bookmark_methods_test.go:136:11: ST1023: should omit type BookmarkList from declaration; it will be inferred from the right-hand side (staticcheck)
  	var list BookmarkList = tabs
  	         ^
  Error: bookmark_methods_test.go:146:11: ST1023: should omit type BookmarkList from declaration; it will be inferred from the right-hand side (staticcheck)
  	var list BookmarkList = tabs
  	         ^
  Error: bookmark_model.go:188:5: QF1001: could apply De Morgan's law (staticcheck)
  	if !(first && t.Name == "") {
  	   ^
  Error: cmd/gobookmarks/db_reset_password_command.go:8:2: ST1001: should not use dot imports (staticcheck)
  	. "github.com/arran4/gobookmarks"
  	^
  Error: cmd/gobookmarks/db_users_command.go:7:2: ST1001: should not use dot imports (staticcheck)
  	. "github.com/arran4/gobookmarks"
  	^
  Error: cmd/gobookmarks/main.go:9:2: ST1001: should not use dot imports (staticcheck)
  	. "github.com/arran4/gobookmarks"
  	^
  Error: cmd/gobookmarks/serve.go:480:4: SA4020: unreachable case clause: net/http.Handler will always match before net/http.HandlerFunc (staticcheck)
  			case http.HandlerFunc:
  			^
  Error: cmd/gobookmarks/test_verification_template_command.go:152:9: SA9003: empty branch (staticcheck)
  	} else {
  	       ^
  Error: config.go:7:2: SA1019: "io/ioutil" has been deprecated since Go 1.19: As of Go 1.16, the same functionality is now provided by package [io] or package [os], and those implementations should be preferred in new code. See the specific function documentation for details. (staticcheck)
  	"io/ioutil"
  	^
  Error: provider_github.go:53:12: SA1019: github.NewEnterpriseClient is deprecated: Use NewClient(httpClient).WithOptions(WithEnterpriseURLs(baseURL, uploadURL)) instead. (staticcheck)
  	c, err := github.NewEnterpriseClient(server+"/api/v3/", server+"/upload/v3/", httpClient)
  	          ^
  Error: provider_github.go:153:99: SA4009: argument branch is overwritten before first use (staticcheck)
  func (p GitHubProvider) getDefaultBranch(ctx context.Context, user string, client *github.Client, branch string) (string, error) {
                                                                                                    ^
  Error: provider_github.go:163:3: SA4009(related information): assignment to branch (staticcheck)
  		branch = *rep.DefaultBranch
  		^
  Error: provider_gitlab.go:56:53: SA1019: gitlab.Client is deprecated: use gitlab.com/gitlab-org/api/client-go instead. See https://gitlab.com/gitlab-org/api/client-go (staticcheck)
  func (GitLabProvider) client(token *oauth2.Token) (*gitlab.Client, error) {
                                                      ^
  Error: provider_gitlab.go:61:9: SA1019: gitlab.NewOAuthClient is deprecated: This module has been migrated to gitlab.com/gitlab-org/api/client-go. See https://gitlab.com/gitlab-org/api/client-go (staticcheck)
  	return gitlab.NewOAuthClient(token.AccessToken, gitlab.WithBaseURL(server))
  	       ^
  Error: provider_gitlab.go:185:82: SA1019: gitlab.Client is deprecated: use gitlab.com/gitlab-org/api/client-go instead. See https://gitlab.com/gitlab-org/api/client-go (staticcheck)
  func (GitLabProvider) getDefaultBranch(ctx context.Context, user string, client *gitlab.Client, branch string) (string, error) {
                                                                                   ^
  Error: provider_gitlab.go:203:3: SA4009(related information): assignment to branch (staticcheck)
  		branch = p.DefaultBranch
  		^
  Error: authHandlers.go:109:7: type ErrorData is unused (unused)
  	type ErrorData struct {
  	     ^
  Error: autoRefreshPage.go:27:6: func taskRedirectWithoutQueryArgs is unused (unused)
  func taskRedirectWithoutQueryArgs(w http.ResponseWriter, r *http.Request) {
       ^
  Error: bookmark_model.go:567:6: func indexAfterColumn is unused (unused)
  func indexAfterColumn(tabs BookmarkList, page *BookmarkPage, colIdx int) int {
       ^
  Error: provider_access.go:55:6: func setCachedBookmarks is unused (unused)
  func setCachedBookmarks(user, ref, bookmarks, sha string) {
       ^
  43 issues:
  * errcheck: 17
  * ineffassign: 3
  * staticcheck: 19
  * unused: 4
  
  Error: issues found