feat: provider-strict configs, slot-based templates, broadcast targets, email bots, command templates

Major architectural improvements:
- Provider-type enforcement: configs validated against provider type at assignment
- TemplateConfig migrated to slot-based pattern (TemplateSlot child table)
- Broadcast targets: TargetReceiver child table for multi-receiver dispatch
- EmailBot: first-class email sender entity with SMTP config, test connection
- CommandTemplateConfig: generic slot-based command response templates
- Provider capability registry: dynamic slot/event/command definitions per provider
- CommandTracker play/pause button matches NotificationTracker style

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

@@ -210,11 +210,6 @@
 				</select>
 			</div>
 
-			<label class="flex items-center gap-2 text-sm cursor-pointer">
-				<input type="checkbox" bind:checked={form.enabled} />
-				{t('commandTracker.enabled')}
-			</label>
-
 			<button type="submit" disabled={submitting}
 				class="px-4 py-2 bg-[var(--color-primary)] text-[var(--color-primary-foreground)] rounded-md text-sm font-medium hover:opacity-90 disabled:opacity-50">
 				{submitting ? t('common.loading') : (editing ? t('common.save') : t('common.create'))}
@@ -252,10 +247,7 @@
 					</div>
 					<div class="flex items-center gap-1">
 						<IconButton icon="mdiPencil" title={t('common.edit')} onclick={() => editTracker(trk)} />
-						<button onclick={() => toggleEnabled(trk)} disabled={toggling[trk.id]}
-							class="text-xs px-2 py-1 rounded-md border border-[var(--color-border)] hover:bg-[var(--color-muted)] disabled:opacity-50">
-							{trk.enabled ? t('notificationTracker.pause') : t('notificationTracker.resume')}
-						</button>
+						<IconButton icon={trk.enabled ? 'mdiPause' : 'mdiPlay'} title={trk.enabled ? t('notificationTracker.pause') : t('notificationTracker.resume')} onclick={() => toggleEnabled(trk)} disabled={toggling[trk.id]} />
 						<button onclick={() => toggleListeners(trk.id)}
 							class="text-xs text-[var(--color-muted-foreground)] hover:underline px-2 py-1">
 							{t('commandTracker.listeners')} {expandedTracker === trk.id ? '▲' : '▼'}