Enable contenthash in filename for dynamic assets (#20813)

This should solve the main problem of dynamic assets getting stale after
a version upgrade. Everything not affected will use query-string based
cache busting, which includes files loaded via HTML or worker scripts.

templates/base/head_script.tmpl

@@ -9,6 +9,7 @@ If you introduce mistakes in it, Gitea JavaScript code wouldn't run correctly.
 		appVer: '{{AppVer}}',
 		appUrl: '{{AppUrl}}',
 		appSubUrl: '{{AppSubUrl}}',
+		assetVersionEncoded: encodeURIComponent('{{AssetVersion}}'), // will be used in URL construction directly
 		assetUrlPrefix: '{{AssetUrlPrefix}}',
 		runModeIsProd: {{.RunModeIsProd}},
 		customEmojis: {{CustomEmojis}},