feat(analytics): add optional Aptabase event tracking UI

Integrate Aptabase analytics via a Tauri plugin and add a privacy
notice flow plus a settings dialog to control whether anonymous
usage events are sent. The app now tracks key user actions while
ensuring analytics never blocks core Git operations.

- Add analytics tracking helper and Aptabase plugin wiring
- Persist analytics consent in localStorage and gate tracking
- Introduce notice and settings dialogs, plus new event calls

src/lib/analytics.ts

@@ -0,0 +1,12 @@
+import { invoke } from "@tauri-apps/api/core";
+
+export type AnalyticsEventProperties = Record<string, string | number>;
+
+export function trackAnalyticsEvent(name: string, props?: AnalyticsEventProperties) {
+  void invoke("plugin:aptabase|track_event", {
+    name,
+    props: props && Object.keys(props).length > 0 ? props : undefined,
+  }).catch(() => {
+    // Analytics must never interrupt the Git workflow.
+  });
+}