refactor: serve site manifest via /assets/site-manifest.json endpoint (#37405)

Slightly reduce the page size for every request, and don't need to use `href="data:`

Signed-off-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: wxiaoguang <2114189+wxiaoguang@users.noreply.github.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Claude (Opus 4.7) <noreply@anthropic.com>

services/context/context.go

@@ -205,7 +205,6 @@ func Contexter() func(next http.Handler) http.Handler {
 			ctx.Data["DisableStars"] = setting.Repository.DisableStars
 			ctx.Data["EnableActions"] = setting.Actions.Enabled && !unit.TypeActions.UnitGlobalDisabled()
 
-			ctx.Data["ManifestData"] = setting.ManifestData
 			ctx.Data["AllLangs"] = translation.AllLangs()
 
 			next.ServeHTTP(ctx.Resp, ctx.Req)