feat(hikes): clickable tag chips + tag filter on the overview

Detail-page tag chips become anchor links to `/hikes?tag=<name>`.
HikesFilterBar grows a tags fieldset (sorted by frequency, with the
hash prefix the chips use) so the user can keep narrowing from there.

Multi-tag filtering is OR — a hike matching any selected tag stays
visible. AND would shrink the listing fast given how few tags most
hikes carry; OR matches what "show me more like this" feels like.

The overview page reads `tag` query params on mount and pre-fills the
filter — supports repeated params (`?tag=winter&tag=easy`).

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "homepage",
-	"version": "1.75.2",
+	"version": "1.75.3",
 	"private": true,
 	"type": "module",
 	"scripts": {

src/lib/components/hikes/HikesFilterBar.svelte

@@ -9,6 +9,7 @@
 		maxLossM: number;
 		difficulties: SvelteSet<Difficulty>;
 		regions: SvelteSet<string>;
+		tags: SvelteSet<string>;
 	};
 
 	interface Props {
@@ -37,6 +38,22 @@
 		return out.sort((a, b) => a.localeCompare(b));
 	});
 
+	// Tags sorted by usage frequency (most-used first), alphabetical for
+	// ties. Frequency ordering surfaces broadly-applicable filters like
+	// "winter" or "easy" at the head of the list, where they're most
+	// useful for narrowing the listing.
+	const tags = $derived.by(() => {
+		const counts = new Map<string, number>();
+		for (const h of hikes) {
+			for (const t of h.tags ?? []) {
+				counts.set(t, (counts.get(t) ?? 0) + 1);
+			}
+		}
+		return [...counts.entries()]
+			.sort((a, b) => b[1] - a[1] || a[0].localeCompare(b[0]))
+			.map(([t]) => t);
+	});
+
 	function toggleDifficulty(d: Difficulty) {
 		if (filter.difficulties.has(d)) filter.difficulties.delete(d);
 		else filter.difficulties.add(d);
@@ -47,6 +64,11 @@
 		else filter.regions.add(r);
 	}
 
+	function toggleTag(t: string) {
+		if (filter.tags.has(t)) filter.tags.delete(t);
+		else filter.tags.add(t);
+	}
+
 	function resetFilters() {
 		filter.maxDistanceKm = maxDistance;
 		filter.maxDurationMin = maxDuration;
@@ -54,6 +76,7 @@
 		filter.maxLossM = maxLoss;
 		filter.difficulties.clear();
 		filter.regions.clear();
+		filter.tags.clear();
 	}
 </script>
 
@@ -149,6 +172,24 @@
 
 		<button type="button" class="reset" onclick={resetFilters}>Zurücksetzen</button>
 	</div>
+
+	{#if tags.length > 0}
+		<fieldset class="tags-fieldset">
+			<legend>Schlagwörter</legend>
+			<div class="pills">
+				{#each tags as t (t)}
+					<button
+						type="button"
+						class="pill pill-tag"
+						class:active={filter.tags.has(t)}
+						onclick={() => toggleTag(t)}
+					>
+						<span class="pill-tag-hash" aria-hidden="true">#</span>{t}
+					</button>
+				{/each}
+			</div>
+		</fieldset>
+	{/if}
 </aside>
 
 <style>
@@ -254,4 +295,26 @@
 	.reset:hover {
 		background: var(--color-bg-elevated);
 	}
+
+	/* Tags fieldset spans the full filter-bar width — there can be many
+	 * (every word an author uses), and forcing it into a column with the
+	 * single-line region/difficulty groups makes them all unreadable. */
+	.tags-fieldset {
+		margin-top: 1rem;
+	}
+
+	.pill-tag {
+		display: inline-flex;
+		align-items: baseline;
+		gap: 0.2rem;
+	}
+
+	.pill-tag-hash {
+		opacity: 0.55;
+		font-weight: 600;
+	}
+
+	.pill-tag.active .pill-tag-hash {
+		opacity: 0.85;
+	}
 </style>

src/routes/hikes/+page.svelte

@@ -1,5 +1,6 @@
 <script lang="ts">
 	import { SvelteSet } from 'svelte/reactivity';
+	import { page } from '$app/state';
 	import HikeCard from '$lib/components/hikes/HikeCard.svelte';
 	import HikesFilterBar, { type HikesFilter } from '$lib/components/hikes/HikesFilterBar.svelte';
 	import HikesOverviewMap from '$lib/components/hikes/HikesOverviewMap.svelte';
@@ -54,7 +55,19 @@
 		maxGainM: Number.POSITIVE_INFINITY,
 		maxLossM: Number.POSITIVE_INFINITY,
 		difficulties: new SvelteSet<Difficulty>(),
-		regions: new SvelteSet<string>()
+		regions: new SvelteSet<string>(),
+		tags: new SvelteSet<string>()
+	});
+
+	// Tag deep-link: arrival from a detail-page tag chip (`/hikes?tag=winter`)
+	// or any saved URL with `?tag=...` pre-selects those tags. Repeated
+	// params accumulate (`?tag=winter&tag=easy`). Only runs on the client —
+	// SSR has no searchParams to read here.
+	$effect(() => {
+		if (typeof window === 'undefined') return;
+		const params = page.url.searchParams.getAll('tag');
+		if (params.length === 0) return;
+		for (const t of params) if (t) filter.tags.add(t);
 	});
 
 	// One-shot per mount: set the slider ceilings to the actual data maxes.
@@ -82,6 +95,17 @@
 			if (h.elevationLossM > filter.maxLossM) continue;
 			if (filter.difficulties.size > 0 && !filter.difficulties.has(h.difficulty)) continue;
 			if (filter.regions.size > 0 && (!h.region || !filter.regions.has(h.region))) continue;
+			// Multi-tag = OR (a hike matching ANY selected tag is shown). AND
+			// would shrink the listing to ~zero quickly given how few tags
+			// most hikes have; OR matches how detail-page chips feel like
+			// "show me more like this".
+			if (filter.tags.size > 0) {
+				let any = false;
+				for (const t of h.tags) {
+					if (filter.tags.has(t)) { any = true; break; }
+				}
+				if (!any) continue;
+			}
 			out.push(h);
 		}
 		return out;

src/routes/hikes/[slug]/+page.svelte

@@ -424,10 +424,14 @@
 	{#if hike.tags.length > 0}
 		<!-- Tag chips sit between the metric tiles (facts) and the
 		     elevation profile (data viz) so they read as framing context —
-		     "what kind of hike is this" — before the data takes over. -->
+		     "what kind of hike is this" — before the data takes over.
+		     Each chip is an anchor link to the /hikes overview with that
+		     tag pre-selected in the filter bar. -->
 		<section class="tags" aria-label="Schlagwörter">
 			{#each hike.tags as tag (tag)}
-				<span class="tag-chip"><span class="tag-hash" aria-hidden="true">#</span>{tag}</span>
+				<a class="tag-chip" href="/hikes?tag={encodeURIComponent(tag)}">
+					<span class="tag-hash" aria-hidden="true">#</span>{tag}
+				</a>
 			{/each}
 		</section>
 	{/if}
@@ -768,6 +772,17 @@
 		background: var(--color-bg-tertiary);
 		border-radius: var(--radius-pill);
 		letter-spacing: 0.005em;
+		text-decoration: none;
+		transition:
+			color var(--transition-fast),
+			background-color var(--transition-fast),
+			scale var(--transition-fast);
+	}
+
+	.tag-chip:hover {
+		color: var(--color-primary);
+		background: var(--color-bg-elevated);
+		scale: 1.05;
 	}
 
 	.tag-hash {
@@ -775,6 +790,10 @@
 		font-weight: 600;
 	}
 
+	.tag-chip:hover .tag-hash {
+		color: color-mix(in oklab, var(--color-primary) 60%, currentColor);
+	}
+
 	.elev-area {
 		padding: 0 1rem;
 		margin-top: 0.25rem;