feat: entity relationship refactor — notification trackers, command system, chat actions

Rework entity schema: rename Tracker→NotificationTracker, add CommandConfig/
CommandTracker/CommandTrackerListener entities for decoupled command handling.
Commands now resolve through CommandTracker→CommandConfig instead of
TelegramBot.commands_config. Smart ref-counted bot polling based on active
listeners. Add chat_action to telegram targets. Full frontend CRUD pages
for command configs and command trackers. Idempotent SQLite migrations.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/routes/+page.svelte

@@ -127,6 +127,9 @@
 				animateCount(0, status.trackers.active, (v) => displayActive = v);
 				animateCount(0, status.trackers.total, (v) => displayTotal = v);
 				animateCount(0, status.targets, (v) => displayTargets = v);
+				if (status.command_trackers !== undefined) {
+					animateCount(0, status.command_trackers, (v) => displayCommandTrackers = v);
+				}
 			}, 200);
 		} catch (err: any) {
 			error = err.message || t('common.error');
@@ -135,10 +138,13 @@
 		}
 	}
 
+	let displayCommandTrackers = $state(0);
+
 	const statCards = $derived(status ? [
 		{ icon: 'mdiServer', label: 'dashboard.providers', value: displayProviders, color: '#0d9488' },
 		{ icon: 'mdiRadar', label: 'dashboard.activeTrackers', value: displayActive, suffix: ` / ${displayTotal}`, color: '#6366f1' },
 		{ icon: 'mdiTarget', label: 'dashboard.targets', value: displayTargets, color: '#f59e0b' },
+		...(status.command_trackers !== undefined ? [{ icon: 'mdiConsoleLine', label: 'nav.commandTrackers', value: displayCommandTrackers, color: '#8b5cf6' }] : []),
 	] : []);
 
 	function timeAgo(dateStr: string): string {