Also restore %3A to : in Matrix room ID URL path

Matrix room IDs are of the form !localpart:server. Both ! and : are
valid unencoded path segment characters per RFC 3986, but url.PathEscape
encodes both. Restore : alongside ! so the full room ID is preserved.

Co-Authored-By: Nicolas <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: bircni

routers/web/repo/setting/webhook.go

@@ -454,8 +454,13 @@ func matrixHookParams(ctx *context.Context) webhookParams {
 	form := web.GetForm(ctx).(*forms.NewMatrixHookForm)
 
 	return webhookParams{
-		Type:        webhook_module.MATRIX,
-		URL:         fmt.Sprintf("%s/_matrix/client/r0/rooms/%s/send/m.room.message", form.HomeserverURL, strings.ReplaceAll(url.PathEscape(form.RoomID), "%21", "!")),
+		Type: webhook_module.MATRIX,
+		// Matrix room IDs are of the form "!localpart:server", where "!" and ":" are
+		// valid unencoded path segment characters per RFC 3986, but url.PathEscape
+		// encodes them. Restore them so Matrix homeservers can recognise the room ID.
+		// See https://spec.matrix.org/latest/appendices/#room-ids
+		URL: fmt.Sprintf("%s/_matrix/client/r0/rooms/%s/send/m.room.message", form.HomeserverURL,
+			strings.NewReplacer("%21", "!", "%3A", ":").Replace(url.PathEscape(form.RoomID))),
 		ContentType: webhook.ContentTypeJSON,
 		HTTPMethod:  http.MethodPut,
 		WebhookForm: form.WebhookForm,