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/targets/+page.svelte

@@ -93,7 +93,11 @@
 
 	let allTargets = $derived(targetsCache.items);
 	let activeType = $derived(page.url.searchParams.get('type') as TargetType | null);
-	let targets = $derived(activeType ? allTargets.filter(t => t.type === activeType) : allTargets);
+	let filterText = $state('');
+	let targets = $derived(allTargets.filter(t =>
+		(!activeType || t.type === activeType) &&
+		(!filterText || t.name.toLowerCase().includes(filterText.toLowerCase()))
+	));
 	let telegramBots = $derived(telegramBotsCache.items);
 	let emailBots = $derived(emailBotsCache.items);
 	let matrixBots = $derived(matrixBotsCache.items);
@@ -479,10 +483,21 @@
 	</div>
 {/if}
 
-{#if targets.length === 0 && !showForm}
+{#if !showForm && allTargets.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)]" />
+</div>
+{/if}
+
+{#if allTargets.length === 0 && !showForm}
 	<Card>
 		<EmptyState icon="mdiTarget" message={t('targets.noTargets')} />
 	</Card>
+{:else if targets.length === 0 && !showForm}
+	<Card>
+		<EmptyState icon="mdiFilterOff" message={t('common.noFilterResults')} />
+	</Card>
 {:else}
 	<div class="space-y-3 stagger-children">
 		{#each targets as target (target.id)}
@@ -547,11 +562,14 @@
 						<div in:slide={{ duration: 150 }} class="mt-2 p-2 rounded-md border border-[var(--color-border)] bg-[var(--color-background)]">
 							{#if target.type === 'telegram'}
 								{@const botId = target.config?.bot_id}
+								{@const existingKeys = new Set((target.receivers || []).map((r: TargetReceiver) => r.receiver_key))}
 								{@const chatItems = (receiverBotChats[botId] || []).map((c: TelegramChat) => ({
 									value: c.chat_id,
 									label: c.title || c.username || c.chat_id,
 									icon: c.type === 'private' ? 'mdiAccount' : c.type === 'channel' ? 'mdiBullhorn' : 'mdiAccountGroup',
 									desc: `${c.type} · ${c.chat_id}`,
+									disabled: existingKeys.has(c.chat_id),
+									disabledHint: existingKeys.has(c.chat_id) ? t('targets.alreadyAdded') : undefined,
 								}))}
 								{#if chatItems.length > 0}
 									<EntitySelect items={chatItems} bind:value={receiverForm.chat_id} placeholder={t('telegramBot.selectChat')} />