fix(onboarding): fix widget links, isComplete logic, and event slugs

Use dynamic href for external links, check completedAt for graduation,
link events by slug instead of _id, and remove stale click handler.

app/components/OnboardingWidget.vue

@@ -19,7 +19,7 @@
           </NuxtLink>
           <a
             v-else-if="currentSuggestion.isExternal"
-            href="https://wiki.ghostguild.org"
+            :href="currentSuggestion.action"
             target="_blank"
             rel="noopener"
             class="btn btn-primary ow-action"
@@ -83,7 +83,6 @@
             target="_blank"
             rel="noopener"
             class="ow-rec-link"
-            @click="trackGoal('wikiClicked')"
           >
             {{ currentSuggestion.actionText }} &rarr;
           </a>