feat: default tracker configs, email validation, expandable target links

- Tracker now has default_tracking_config_id and default_template_config_id
  that apply to all linked targets unless overridden per-target
- Dispatch falls back to tracker defaults when per-link configs are null
- Email bot creation validates SMTP connection before saving
- Email notifications sent as HTML (links render properly)
- Linked target items are expandable: collapsed shows config CrossLinks,
  expanded shows config selectors; action buttons always visible
- Fix email bot test button icon (mdiEmailSend → mdiSend)
- Fix target type icons in LinkedTargetsSection for all types
- Provider filter moved above search in sidebar

frontend/src/routes/+layout.svelte

@@ -35,10 +35,12 @@
 		...allProviders.map(p => ({ value: p.id, icon: providerDefaultIcon(p), label: p.name, desc: p.type })),
 	]);
 	let providerFilterValue = $state(globalProviderFilter.id ?? 0);
+	let _syncingFilter = false;
 
 	// Sync filter value → store
 	$effect(() => {
 		const v = providerFilterValue;
+		if (_syncingFilter) return;
 		globalProviderFilter.set(v === 0 ? null : v);
 	});
 
@@ -46,7 +48,9 @@
 	$effect(() => {
 		const storeId = globalProviderFilter.id;
 		if (storeId === null && providerFilterValue !== 0) {
+			_syncingFilter = true;
 			providerFilterValue = 0;
+			_syncingFilter = false;
 		}
 	});
 
@@ -85,6 +89,11 @@
 			ptype ? items.filter(i => i.provider_type === ptype) : items;
 
 		const targets = targetsCache.items;
+		// Single pass to count targets by type
+		const targetsByType = new Map<string, number>();
+		for (const t of targets) {
+			targetsByType.set(t.type, (targetsByType.get(t.type) || 0) + 1);
+		}
 		return {
 			providers: pid ? 1 : providersCache.items.length,
 			notification_trackers: filterById(notificationTrackersCache.items as any[]).length,
@@ -97,14 +106,14 @@
 			telegram_bots: telegramBotsCache.items.length,
 			email_bots: emailBotsCache.items.length,
 			matrix_bots: matrixBotsCache.items.length,
-			targets_telegram: targets.filter(t => t.type === 'telegram').length,
-			targets_webhook: targets.filter(t => t.type === 'webhook').length,
-			targets_email: targets.filter(t => t.type === 'email').length,
-			targets_discord: targets.filter(t => t.type === 'discord').length,
-			targets_slack: targets.filter(t => t.type === 'slack').length,
-			targets_ntfy: targets.filter(t => t.type === 'ntfy').length,
-			targets_matrix: targets.filter(t => t.type === 'matrix').length,
-			targets_broadcast: targets.filter(t => t.type === 'broadcast').length,
+			targets_telegram: targetsByType.get('telegram') || 0,
+			targets_webhook: targetsByType.get('webhook') || 0,
+			targets_email: targetsByType.get('email') || 0,
+			targets_discord: targetsByType.get('discord') || 0,
+			targets_slack: targetsByType.get('slack') || 0,
+			targets_ntfy: targetsByType.get('ntfy') || 0,
+			targets_matrix: targetsByType.get('matrix') || 0,
+			targets_broadcast: targetsByType.get('broadcast') || 0,
 		} as Record<string, number>;
 	});