Issue time estimate, meaningful time tracking (#23113)

Redesign the time tracker side bar, and add "time estimate" support (in "1d 2m" format)

Closes #23112

---------

Co-authored-by: stuzer05 <stuzer05@gmail.com>
Co-authored-by: Yarden Shoham <hrsi88@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/web/repo/issue_stopwatch.go

@@ -4,7 +4,6 @@
 package repo
 
 import (
-	"net/http"
 	"strings"
 
 	"code.gitea.io/gitea/models/db"
@@ -40,8 +39,7 @@ func IssueStopwatch(c *context.Context) {
 		c.Flash.Success(c.Tr("repo.issues.tracker_auto_close"))
 	}
 
-	url := issue.Link()
-	c.Redirect(url, http.StatusSeeOther)
+	c.JSONRedirect("")
 }
 
 // CancelStopwatch cancel the stopwatch
@@ -72,8 +70,7 @@ func CancelStopwatch(c *context.Context) {
 		})
 	}
 
-	url := issue.Link()
-	c.Redirect(url, http.StatusSeeOther)
+	c.JSONRedirect("")
 }
 
 // GetActiveStopwatch is the middleware that sets .ActiveStopwatch on context