fix: prevent duplicate prestige bot announcements on concurrent requests

Adds an optimistic lock on the prestige route so that a second concurrent
request for the same state is rejected with 409 rather than firing the
Discord announcement twice. Also adds missing branch-coverage tests for
debug.ts to satisfy the 100% threshold.

Closes #162

apps/api/test/routes/prestige.spec.ts

@@ -8,7 +8,7 @@ import type { GameState } from "@elysium/types";
 vi.mock("../../src/db/client.js", () => ({
   prisma: {
     player: { update: vi.fn() },
-    gameState: { findUnique: vi.fn(), update: vi.fn() },
+    gameState: { findUnique: vi.fn(), update: vi.fn(), updateMany: vi.fn() },
   },
 }));
 
@@ -48,7 +48,7 @@ describe("prestige route", () => {
   let app: Hono;
   let prisma: {
     player: { update: ReturnType<typeof vi.fn> };
-    gameState: { findUnique: ReturnType<typeof vi.fn>; update: ReturnType<typeof vi.fn> };
+    gameState: { findUnique: ReturnType<typeof vi.fn>; update: ReturnType<typeof vi.fn>; updateMany: ReturnType<typeof vi.fn> };
   };
 
   beforeEach(async () => {
@@ -83,8 +83,8 @@ describe("prestige route", () => {
 
     it("returns runestones on successful prestige", async () => {
       const state = makeState();
-      vi.mocked(prisma.gameState.findUnique).mockResolvedValueOnce({ state } as never);
-      vi.mocked(prisma.gameState.update).mockResolvedValueOnce({} as never);
+      vi.mocked(prisma.gameState.findUnique).mockResolvedValueOnce({ state, updatedAt: 0 } as never);
+      vi.mocked(prisma.gameState.updateMany).mockResolvedValueOnce({ count: 1 } as never);
       vi.mocked(prisma.player.update).mockResolvedValueOnce({} as never);
       const res = await post("");
       expect(res.status).toBe(200);
@@ -93,6 +93,14 @@ describe("prestige route", () => {
       expect(body.runestones).toBeGreaterThanOrEqual(0);
     });
 
+    it("returns 409 when a concurrent prestige already committed", async () => {
+      const state = makeState();
+      vi.mocked(prisma.gameState.findUnique).mockResolvedValueOnce({ state, updatedAt: 0 } as never);
+      vi.mocked(prisma.gameState.updateMany).mockResolvedValueOnce({ count: 0 } as never);
+      const res = await post("");
+      expect(res.status).toBe(409);
+    });
+
     it("returns 500 when the database throws during prestige", async () => {
       vi.mocked(prisma.gameState.findUnique).mockRejectedValueOnce(new Error("DB error"));
       const res = await post("");
@@ -112,8 +120,8 @@ describe("prestige route", () => {
           challenges: [{ id: "prestige_challenge", type: "prestige", target: 2, progress: 0, completed: false, crystalReward: 5 }],
         } as GameState["dailyChallenges"],
       });
-      vi.mocked(prisma.gameState.findUnique).mockResolvedValueOnce({ state } as never);
-      vi.mocked(prisma.gameState.update).mockResolvedValueOnce({} as never);
+      vi.mocked(prisma.gameState.findUnique).mockResolvedValueOnce({ state, updatedAt: 0 } as never);
+      vi.mocked(prisma.gameState.updateMany).mockResolvedValueOnce({ count: 1 } as never);
       vi.mocked(prisma.player.update).mockResolvedValueOnce({} as never);
       const res = await post("");
       expect(res.status).toBe(200);