Fix mobile header layout, add resumable progress + coin wallet

Header nav was splitting into three lines on mobile (logo / nav /
logout floating right with a big gap) — applied the same order-last
wrap pattern already proven in top-tickets/project-claude, so nav
drops to its own scrollable row instead.

Bigger feature: player progress now survives closing the tab, for all
three templates, not just Clicker. Each Phaser scene reports its state
through the same registry-callback pattern already used for onFinish
(onProgress), and reads an initialState to resume instead of always
starting fresh. Autosave fires every 10 minutes for free; an instant
manual save costs coins.

New coin economy (src/lib/wallet/): a wallet + transaction ledger per
user, atomic grant/spend via db.transaction() so two concurrent spends
against a low balance can't both succeed (verified with a real race
test — exactly one wins, balance never goes negative). New accounts
get a 20-coin signup bonus so manual save is testable before any real
payment method exists.

Real-money purchases are scaffolded but deliberately not wired to a
provider yet — user hasn't picked one. /api/wallet/purchase creates a
pending order and returns a clean "not configured" error, same shape
as the AI/LDAP not-configured responses elsewhere in this project. The
payment abstraction (src/lib/payments/provider.ts) is the one seam a
real adapter needs to fill in later.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QcXH24ky6zjk2UyK5oZUPH

src/app/api/wallet/route.ts

@@ -0,0 +1,17 @@
+export const runtime = "nodejs";
+
+import { NextResponse } from "next/server";
+import { requireSession } from "@/lib/auth/require";
+import { getBalance, listRecentTransactions } from "@/lib/wallet/service";
+
+export async function GET() {
+  const { session, response } = await requireSession();
+  if (!session) return response;
+
+  const [balance, transactions] = await Promise.all([
+    getBalance(session.user.id),
+    listRecentTransactions(session.user.id),
+  ]);
+
+  return NextResponse.json({ balance, transactions });
+}