feat(planner): show yellow neutral badge for scoreDelta = 0 in RecipePicker

Neutral suggestions (no variety impact) now show "= 0.0 Punkte" in yellow
instead of no badge, making the three states explicit: green (improves),
yellow (neutral), red (worsens).

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

frontend/src/lib/planner/RecipePicker.svelte

@@ -120,6 +120,14 @@
 						>
 							↓ {(suggestion.scoreDelta ?? 0).toFixed(1)} Punkte
 						</span>
+					{:else}
+						<span
+							data-testid="badge-{suggestion.recipe.id}"
+							data-type="neutral"
+							style="display: inline-block; margin-top: 3px; font-size: 9px; font-weight: 500; padding: 1px 5px; border-radius: 3px; background: var(--yellow-tint); color: var(--yellow-text);"
+						>
+							= {(suggestion.scoreDelta ?? 0).toFixed(1)} Punkte
+						</span>
 					{/if}
 				</div>
 				<button