fix(planner): guard scoreDelta against undefined in RecipePicker badge

Defensive null-coalescing prevents crash when suggestion data arrives
without scoreDelta (e.g. stale backend or mismatched schema).

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

frontend/src/lib/planner/RecipePicker.svelte

@@ -121,7 +121,7 @@
 							data-type="good"
 							style="display: inline-block; margin-top: 3px; font-size: 8px; font-weight: 500; padding: 1px 5px; border-radius: 3px; background: var(--green-tint); color: var(--green-dark);"
 						>
-							↑ +{suggestion.scoreDelta.toFixed(0)} Punkte
+							↑ +{(suggestion.scoreDelta ?? 0).toFixed(0)} Punkte
 						</span>
 					{:else}
 						<span