fix: {show,link to} proper PR on kanban board ref (#15004)

the issue was that PR references in kanban boards were being generated
using `.ID` instead of `.Index`, which led to constructing incorrect
links to possibly non-existent {PR,issue}s and following that to showing
nonsensical values in the boards.

kudos also go to @zeripath for pointing at the file to fix.

Signed-off-by: wULLSnpAXbWZGYDYyhWTKKspEQoaYxXyhoisqHf <a_mirre@utb.cz>
Co-authored-by: zeripath <art27@cantab.net>

templates/repo/projects/view.tmpl

@@ -175,9 +175,9 @@
 							{{- end }}
 							{{- range index $.LinkedPRs .ID }}
 							<div class="meta">
-								<a href="{{$.RepoLink}}/pulls/{{ .ID }}">
+								<a href="{{$.RepoLink}}/pulls/{{ .Index }}">
 									<span class="{{if .PullRequest.HasMerged}}purple{{else if .IsClosed}}red{{else}}green{{end}}">{{svg "octicon-git-merge"}}</span>
-									{{ .Title}} (#{{ .ID }})
+									{{ .Title}} (#{{ .Index }})
 								</a>
 							</div>
 							{{- end }}