Instance-wide (global) info banner and maintenance mode (#36571)

The banner allows site operators to communicate important announcements
(e.g., maintenance windows, policy updates, service notices) directly
within the UI.

The maintenance mode only allows admin to access the web UI.

* Fix #2345
* Fix #9618

---------

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

services/context/context.go

@@ -100,12 +100,12 @@ func GetValidateContext(req *http.Request) (ctx *ValidateContext) {
 	return ctx
 }
 
-func NewTemplateContextForWeb(ctx *Context) TemplateContext {
-	tmplCtx := NewTemplateContext(ctx, ctx.Req)
-	tmplCtx["Locale"] = ctx.Base.Locale
+func NewTemplateContextForWeb(ctx reqctx.RequestContext, req *http.Request, locale translation.Locale) TemplateContext {
+	tmplCtx := NewTemplateContext(ctx, req)
+	tmplCtx["Locale"] = locale
 	tmplCtx["AvatarUtils"] = templates.NewAvatarUtils(ctx)
 	tmplCtx["RenderUtils"] = templates.NewRenderUtils(ctx)
-	tmplCtx["RootData"] = ctx.Data
+	tmplCtx["RootData"] = ctx.GetData()
 	tmplCtx["Consts"] = map[string]any{
 		"RepoUnitTypeCode":            unit.TypeCode,
 		"RepoUnitTypeIssues":          unit.TypeIssues,
@@ -132,7 +132,7 @@ func NewWebContext(base *Base, render Render, session session.Store) *Context {
 		Repo:  &Repository{},
 		Org:   &Organization{},
 	}
-	ctx.TemplateContext = NewTemplateContextForWeb(ctx)
+	ctx.TemplateContext = NewTemplateContextForWeb(ctx, ctx.Base.Req, ctx.Base.Locale)
 	ctx.Flash = &middleware.Flash{DataStore: ctx, Values: url.Values{}}
 	ctx.SetContextValue(WebContextKey, ctx)
 	return ctx