chore: enable forcetypeassert linter, fix issues (#38804)

Enable [`forcetypeassert`](https://github.com/gostaticanalysis/forcetypeassert)
linter to prevent unchecked type assertions. ~650 issues fixed, most
fixes were clean, some use `setting.PanicInDevOrTesting`.

The only behaviour changes are where code would previously send a 500 error
or panic, a 4xx error is now emitted.

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

cmd/admin_auth_smtp.go

@@ -175,12 +175,11 @@ func (a *authService) runUpdateSMTP(ctx context.Context, c *cli.Command) error {
 		return err
 	}
 
-	source, err := a.getAuthSourceByID(ctx, c.Int64("id"))
+	source, err := a.getAuthSourceOfType(ctx, c.Int64("id"), auth_model.SMTP)
 	if err != nil {
 		return err
 	}
-
-	smtpConfig := source.Cfg.(*smtp.Source)
+	smtpConfig := auth_model.MustSourceCfg[*smtp.Source](source)
 
 	if err := parseSMTPConfig(c, smtpConfig); err != nil {
 		return err