feat: use path-based date URLs for nutrition page

Migrate /fitness/nutrition?date=YYYY-MM-DD to /fitness/nutrition/YYYY-MM-DD
using SvelteKit optional param [[date=fitnessDate]]. Replace date nav
buttons with anchor tags for native browser navigation. Today resolves to
the clean /fitness/nutrition path without a date segment.

src/params/fitnessDate.ts

@@ -0,0 +1,5 @@
+import type { ParamMatcher } from '@sveltejs/kit';
+
+export const match: ParamMatcher = (param) => {
+	return /^\d{4}-\d{2}-\d{2}$/.test(param);
+};

src/routes/fitness/+layout.svelte

@@ -64,7 +64,9 @@
 	const activePath = $derived(`/fitness/${s.workout}/${s.active}`);
 	const isOnActivePage = $derived($page.url.pathname === activePath);
 	const isNutritionPage = $derived(
-		$page.url.pathname === `/fitness/${s.nutrition}` || $page.url.pathname === `/fitness/${s.nutrition}/`
+		$page.url.pathname.startsWith(`/fitness/${s.nutrition}`) &&
+		!$page.url.pathname.startsWith(`/fitness/${s.nutrition}/food`) &&
+		!$page.url.pathname.startsWith(`/fitness/${s.nutrition}/meals`)
 	);
 
 	/** @param {number} secs */

src/routes/fitness/[nutrition=fitnessNutrition]/[[date=fitnessDate]]/+page.server.ts

@@ -6,8 +6,8 @@ import { Recipe } from '$models/Recipe';
 import { RoundOffCache } from '$models/RoundOffCache';
 import mongoose from 'mongoose';
 
-export const load: PageServerLoad = async ({ fetch, url, locals }) => {
-	const dateParam = url.searchParams.get('date') || new Date().toISOString().slice(0, 10);
+export const load: PageServerLoad = async ({ fetch, params, locals }) => {
+	const dateParam = params.date || new Date().toISOString().slice(0, 10);
 
 	// Run all independent work in parallel: 3 API calls + workout kcal DB query
 	const dayStart = new Date(dateParam + 'T00:00:00.000Z');

src/routes/fitness/[nutrition=fitnessNutrition]/[[date=fitnessDate]]/+page.svelte

@@ -29,17 +29,17 @@
 		return d.toLocaleDateString(isEn ? 'en-US' : 'de-DE', { weekday: 'short', day: 'numeric', month: 'short' });
 	});
 
-	async function navigateDate(offset) {
+	function dateOffset(offset) {
 		const d = new Date(currentDate + 'T12:00:00');
 		d.setDate(d.getDate() + offset);
-		currentDate = d.toISOString().slice(0, 10);
-		await loadEntries();
+		return d.toISOString().slice(0, 10);
 	}
 
-	async function goToday() {
-		currentDate = todayStr;
-		await loadEntries();
-	}
+	const prevDate = $derived(dateOffset(-1));
+	const nextDate = $derived(dateOffset(1));
+	const prevHref = $derived(prevDate === todayStr ? `/fitness/${s.nutrition}` : `/fitness/${s.nutrition}/${prevDate}`);
+	const nextHref = $derived(nextDate === todayStr ? `/fitness/${s.nutrition}` : `/fitness/${s.nutrition}/${nextDate}`);
+	const todayHref = $derived(`/fitness/${s.nutrition}`);
 
 	// --- Entries ---
 	// svelte-ignore state_referenced_locally
@@ -47,10 +47,6 @@
 	// svelte-ignore state_referenced_locally
 	let recipeImages = $state(data.recipeImages ?? {});
 
-	async function loadEntries() {
-		await goto(`/fitness/${s.nutrition}?date=${currentDate}`, { replaceState: true, noScroll: true });
-	}
-
 	// Keep reactive with server data when navigating
 	$effect(() => {
 		entries = data.foodLog?.entries ?? [];
@@ -748,7 +744,7 @@
 				})
 			});
 
-			await goto(`/fitness/${s.nutrition}?date=${currentDate}`, { replaceState: true, noScroll: true });
+			await goto(`/fitness/${s.nutrition}/${currentDate}`, { replaceState: true, noScroll: true });
 			selectedCmMeal = null;
 			closeFabModal();
 			toast.success(isEn ? `Logged "${meal.name}"` : `"${meal.name}" eingetragen`);
@@ -793,7 +789,7 @@
 				})
 			});
 
-			await goto(`/fitness/${s.nutrition}?date=${currentDate}`, { replaceState: true, noScroll: true });
+			await goto(`/fitness/${s.nutrition}/${currentDate}`, { replaceState: true, noScroll: true });
 			selectedCmMeal = null;
 			cancelAdd();
 			toast.success(isEn ? `Logged "${meal.name}"` : `"${meal.name}" eingetragen`);
@@ -1160,18 +1156,18 @@
 <div class="nutrition-page">
 	<!-- Date Navigator -->
 	<div class="date-nav">
-		<button class="date-btn" onclick={() => navigateDate(-1)} aria-label="Previous day">
+		<a class="date-btn" href={prevHref} aria-label="Previous day" data-sveltekit-replacestate data-sveltekit-noscroll>
 			<ChevronLeft size={20} />
-		</button>
-		<button class="date-display" onclick={goToday} class:is-today={isToday}>
+		</a>
+		<span class="date-display" class:is-today={isToday}>
 			{displayDate}
 			{#if isToday}<span class="today-badge">{t('today', lang)}</span>{/if}
-		</button>
-		<button class="date-btn" onclick={() => navigateDate(1)} aria-label="Next day">
+		</span>
+		<a class="date-btn" href={nextHref} aria-label="Next day" data-sveltekit-replacestate data-sveltekit-noscroll>
 			<ChevronRight size={20} />
-		</button>
+		</a>
 		{#if !isToday}
-			<button class="go-today-btn" onclick={goToday}>{t('today', lang)}</button>
+			<a class="go-today-btn" href={todayHref} data-sveltekit-replacestate data-sveltekit-noscroll>{t('today', lang)}</a>
 		{/if}
 	</div>
 
@@ -1923,6 +1919,7 @@
 		border-radius: 50%;
 		display: flex;
 		align-items: center;
+		text-decoration: none;
 		transition: color 0.15s, background 0.15s;
 	}
 	.date-btn:hover {
@@ -1935,7 +1932,6 @@
 		color: var(--color-text-primary);
 		font-size: 1.05rem;
 		font-weight: 700;
-		cursor: pointer;
 		padding: 0.35rem 0.75rem;
 		border-radius: 8px;
 		display: flex;
@@ -1944,9 +1940,6 @@
 		transition: background 0.15s;
 		letter-spacing: -0.01em;
 	}
-	.date-display:hover {
-		background: var(--color-bg-elevated);
-	}
 	.today-badge {
 		font-size: 0.6rem;
 		font-weight: 700;
@@ -1966,6 +1959,7 @@
 		background: color-mix(in srgb, var(--color-primary) 10%, transparent);
 		border: 1px solid color-mix(in srgb, var(--color-primary) 25%, transparent);
 		padding: 0.25rem 0.6rem;
+		text-decoration: none;
 		border-radius: 6px;
 		cursor: pointer;
 		transition: background 0.15s;