cmd: show detected config path in web command help (#8152)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

cmd/gogs/web.go

@@ -52,7 +52,7 @@ and it takes care of all the other things for you`,
 	Action: runWeb,
 	Flags: []cli.Flag{
 		stringFlag("port, p", "3000", "Temporary port number to prevent conflict"),
-		stringFlag("config, c", "", "Custom configuration file path"),
+		stringFlag("config, c", filepath.Join(conf.CustomDir(), "conf", "app.ini"), "Custom configuration file path"),
 	},
 }