feat: locale-aware notification templates + UX improvements

- Add locale support to notification templates (matching command template
  pattern): TemplateSlot now has locale field with (config_id, slot_name,
  locale) uniqueness, nested API format {slot: {locale: template}}
- Migration merges separate EN/RU system configs into unified per-provider
  configs; seeds create one config per provider with multi-locale slots
- Locale-aware dispatch with EN fallback in NotificationDispatcher
- Frontend locale tabs (EN/RU) on template config editor
- Fix tracking config cards not showing default provider icons
- Global provider filter, search palette, and various UX polish

frontend/src/routes/command-configs/+page.svelte

@@ -17,6 +17,7 @@
 	import EntitySelect from '$lib/components/EntitySelect.svelte';
 	import { snackSuccess, snackError } from '$lib/stores/snackbar.svelte';
 	import { highlightFromUrl } from '$lib/highlight';
+	import { globalProviderFilter } from '$lib/stores/provider-filter.svelte';
 	import type { CommandConfig } from '$lib/types';
 
 	function templateName(id: number | null): string {
@@ -28,9 +29,10 @@
 	let allCmdConfigs = $derived(commandConfigsCache.items);
 	let filterText = $state('');
 	let filterType = $state('');
+	let effectiveType = $derived(globalProviderFilter.providerType || filterType);
 	let configs = $derived(allCmdConfigs.filter(c =>
 		(!filterText || c.name.toLowerCase().includes(filterText.toLowerCase())) &&
-		(!filterType || c.provider_type === filterType)
+		(!effectiveType || c.provider_type === effectiveType)
 	));
 	let cmdTemplateConfigs = $derived(commandTemplateConfigsCache.items);
 	const templateItems = $derived(cmdTemplateConfigs
@@ -240,9 +242,11 @@
 <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)]" />
+	{#if !globalProviderFilter.id}
 	<div class="w-48">
 		<IconGridSelect items={providerTypeFilterItems()} bind:value={filterType} columns={2} compact />
 	</div>
+	{/if}
 </div>
 {/if}