fix(planner): merge recipe tags into slotMap from data.recipes

SlotRecipe from the week-plan API carries no tags, so the protein
gradient lookup in DesktopDayTile always fell through to --color-surface.
Build a recipeById lookup from data.recipes and spread tags onto each
slot's recipe when constructing slotMap.

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

frontend/src/routes/(app)/planner/+page.svelte

@@ -25,7 +25,20 @@
 
 	let days = $derived(weekDays(weekStart));
 	let slots = $derived(weekPlan?.slots ?? []);
-	let slotMap = $derived(Object.fromEntries(slots.map((s: any) => [s.slotDate, s])));
+	// SlotRecipe from the API has no tags — merge from data.recipes by id
+	const recipeById = $derived(
+		Object.fromEntries((data.recipes ?? []).map((r: any) => [r.id, r]))
+	);
+	let slotMap = $derived(
+		Object.fromEntries(
+			slots.map((s: any) => [
+				s.slotDate,
+				s.recipe
+					? { ...s, recipe: { ...s.recipe, tags: recipeById[s.recipe.id]?.tags ?? [] } }
+					: s
+			])
+		)
+	);
 
 	// Default selected day: today if in this week, else first day
 	// We read data.weekStart once synchronously here (before reactivity kicks in) to seed the initial value.