chore: enable forcetypeassert linter, fix issues (#38804)

Enable [`forcetypeassert`](https://github.com/gostaticanalysis/forcetypeassert)
linter to prevent unchecked type assertions. ~650 issues fixed, most
fixes were clean, some use `setting.PanicInDevOrTesting`.

The only behaviour changes are where code would previously send a 500 error
or panic, a 4xx error is now emitted.

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

routers/web/repo/issue_view.go

@@ -499,8 +499,8 @@ func (prInfo *pullRequestViewInfo) prepareMergeBoxCommitSigning(ctx *context.Con
 		data.willSign = sign
 		data.signingKeyMergeDisplay = asymkey_model.GetDisplaySigningKey(key)
 		if err != nil {
-			if asymkey_service.IsErrWontSign(err) {
-				wontSignReason = string(err.(*asymkey_service.ErrWontSign).Reason)
+			if errWontSign, ok := err.(*asymkey_service.ErrWontSign); ok {
+				wontSignReason = string(errWontSign.Reason)
 			} else {
 				wontSignReason = "error"
 				if !errors.Is(err, util.ErrNotExist) {
@@ -560,8 +560,9 @@ func prepareIssueViewSidebarTimeTracker(ctx *context.Context, issue *issues_mode
 
 	if ctx.IsSigned {
 		// Deal with the stopwatch
-		ctx.Data["IsStopwatchRunning"] = issues_model.StopwatchExists(ctx, ctx.Doer.ID, issue.ID)
-		if !ctx.Data["IsStopwatchRunning"].(bool) {
+		isStopwatchRunning := issues_model.StopwatchExists(ctx, ctx.Doer.ID, issue.ID)
+		ctx.Data["IsStopwatchRunning"] = isStopwatchRunning
+		if !isStopwatchRunning {
 			exists, _, swIssue, err := issues_model.HasUserStopwatch(ctx, ctx.Doer.ID)
 			if err != nil {
 				ctx.ServerError("HasUserStopwatch", err)