feat: enforce active quest limit in assignQuest

Adds a limit check to assignQuest that reads maxActiveQuests from game
settings and throws a UserError when the user has reached their active
quest limit. Completed quests are excluded from the count.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

shared/modules/quest/quest.service.test.ts

@@ -75,6 +75,12 @@ describe("questService", () => {
 
     describe("assignQuest", () => {
         it("should assign quest", async () => {
+            const { gameSettingsService } = await import("@shared/modules/game-settings/game-settings.service");
+            const mockGetSettings = spyOn(gameSettingsService, 'getSettings').mockResolvedValue({
+                quest: { maxActiveQuests: 3 },
+            } as any);
+
+            mockFindMany.mockResolvedValue([]); // no active quests
             mockReturning.mockResolvedValue([{ userId: 1n, questId: 101 }]);
 
             const result = await questService.assignQuest("1", 101);
@@ -86,6 +92,47 @@ describe("questService", () => {
                 questId: 101,
                 progress: 0
             });
+
+            mockGetSettings.mockRestore();
+        });
+
+        it("should throw when user has reached active quest limit", async () => {
+            // Mock gameSettingsService to return maxActiveQuests: 2
+            const { gameSettingsService } = await import("@shared/modules/game-settings/game-settings.service");
+            const mockGetSettings = spyOn(gameSettingsService, 'getSettings').mockResolvedValue({
+                quest: { maxActiveQuests: 2 },
+            } as any);
+
+            // User has 2 incomplete quests
+            mockFindMany.mockResolvedValue([
+                { userId: 1n, questId: 1, completedAt: null },
+                { userId: 1n, questId: 2, completedAt: null },
+            ]);
+
+            expect(questService.assignQuest("1", 3)).rejects.toThrow(
+                "You can only have 2 active quests at a time. Complete a quest before accepting a new one."
+            );
+
+            mockGetSettings.mockRestore();
+        });
+
+        it("should allow assignment when completed quests don't count toward limit", async () => {
+            const { gameSettingsService } = await import("@shared/modules/game-settings/game-settings.service");
+            const mockGetSettings = spyOn(gameSettingsService, 'getSettings').mockResolvedValue({
+                quest: { maxActiveQuests: 2 },
+            } as any);
+
+            // User has 2 quests but 1 is completed
+            mockFindMany.mockResolvedValue([
+                { userId: 1n, questId: 1, completedAt: null },
+                { userId: 1n, questId: 2, completedAt: new Date() },
+            ]);
+            mockReturning.mockResolvedValue([{ userId: 1n, questId: 3 }]);
+
+            const result = await questService.assignQuest("1", 3);
+            expect(result).toEqual([{ userId: 1n, questId: 3 }]);
+
+            mockGetSettings.mockRestore();
         });
     });