feat: add filtering to all entity list pages

- Tracking configs: filter by name + provider type
- Template configs: filter by name + provider type
- Command configs: filter by name + provider type
- Notification trackers: filter by name + provider
- Command trackers: filter by name + provider
- Targets: filter by name (type filtering already existed)
- Nav badge counts include system-owned entities (user_id=0)
- Shows "no items match filter" vs "no items yet" empty states

frontend/src/routes/notification-trackers/+page.svelte

@@ -22,7 +22,13 @@
 
 	let loaded = $state(false);
 	let loadError = $state('');
-	let notificationTrackers = $state<Tracker[]>([]);
+	let allNotificationTrackers = $state<Tracker[]>([]);
+	let filterText = $state('');
+	let filterProviderId = $state(0);
+	let notificationTrackers = $derived(allNotificationTrackers.filter(t =>
+		(!filterText || t.name.toLowerCase().includes(filterText.toLowerCase())) &&
+		(!filterProviderId || t.provider_id === filterProviderId)
+	));
 	let providers = $derived(providersCache.items);
 	const providerItems = $derived(providers.map(p => ({ value: p.id, label: p.name, icon: p.icon || 'mdiServer', desc: p.type })));
 	let targets = $derived(targetsCache.items);
@@ -91,7 +97,7 @@
 	async function load() {
 		loadError = '';
 		try {
-			[notificationTrackers] = await Promise.all([
+			[allNotificationTrackers] = await Promise.all([
 				api('/notification-trackers'),
 				providersCache.fetch(), targetsCache.fetch(),
 				trackingConfigsCache.fetch(), templateConfigsCache.fetch(),
@@ -366,10 +372,29 @@
 {/if}
 
 {#if loaded && !loadError}
-{#if notificationTrackers.length === 0 && !showForm}
+
+{#if !showForm && allNotificationTrackers.length > 0}
+<div class="flex items-center gap-2 mb-3">
+	<input type="text" bind:value={filterText} placeholder={t('common.filterByName')}
+		class="flex-1 px-3 py-1.5 border border-[var(--color-border)] rounded-md text-sm bg-[var(--color-background)]" />
+	<select bind:value={filterProviderId}
+		class="px-3 py-1.5 border border-[var(--color-border)] rounded-md text-sm bg-[var(--color-background)]">
+		<option value={0}>{t('common.allProviders')}</option>
+		{#each providers as p}
+			<option value={p.id}>{p.name} ({p.type})</option>
+		{/each}
+	</select>
+</div>
+{/if}
+
+{#if allNotificationTrackers.length === 0 && !showForm}
 	<Card>
 		<EmptyState icon="mdiRadar" message={t('notificationTracker.noTrackers')} />
 	</Card>
+{:else if notificationTrackers.length === 0 && !showForm}
+	<Card>
+		<EmptyState icon="mdiFilterOff" message={t('common.noFilterResults')} />
+	</Card>
 {:else if !showForm}
 	<div class="space-y-3 stagger-children">
 		{#each notificationTrackers as tracker}