feat(onboarding): skippable avatar with first-match prompt and usage-reason pack picks

Lets new users skip the onboarding avatar step and instead defers the ask
to a lightweight, dismissible prompt shown once after the couple's first
match. Also personalizes the home screen's first pack recommendation using
the usage_reason already collected during onboarding, which now round-trips
through GET /v1/me.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

apps/mobile/src/__tests__/lib/avatarPromptSeen.test.ts

@@ -0,0 +1,34 @@
+import { hasSeenAvatarPrompt, markAvatarPromptSeen } from "@/lib/avatarPromptSeen";
+
+jest.mock("expo-secure-store", () => {
+    const store = new Map<string, string>();
+    return {
+        __store: store,
+        getItemAsync: jest.fn(async (key: string) => store.get(key) ?? null),
+        setItemAsync: jest.fn(async (key: string, value: string) => { store.set(key, value); }),
+    };
+});
+
+// eslint-disable-next-line @typescript-eslint/no-var-requires
+const secureStore = require("expo-secure-store") as { __store: Map<string, string> };
+
+describe("avatarPromptSeen", () => {
+    beforeEach(() => {
+        secureStore.__store.clear();
+    });
+
+    it("reports unseen until marked seen for that user", async () => {
+        expect(await hasSeenAvatarPrompt("user-1")).toBe(false);
+
+        await markAvatarPromptSeen("user-1");
+
+        expect(await hasSeenAvatarPrompt("user-1")).toBe(true);
+    });
+
+    it("tracks the seen flag per user, so a shared device does not skip the prompt for a new account", async () => {
+        await markAvatarPromptSeen("user-1");
+
+        expect(await hasSeenAvatarPrompt("user-1")).toBe(true);
+        expect(await hasSeenAvatarPrompt("user-2")).toBe(false);
+    });
+});