feat: Add user existence checks to economy commands and refactor trade service to expose sessions for testing.

src/modules/leveling/leveling.service.test.ts

@@ -77,8 +77,8 @@ describe("levelingService", () => {
             // base 100, exp 1.5
             // lvl 1: 100 * 1^1.5 = 100
             // lvl 2: 100 * 2^1.5 = 100 * 2.828 = 282
-            expect(levelingService.getXpForLevel(1)).toBe(100);
-            expect(levelingService.getXpForLevel(2)).toBe(282);
+            expect(levelingService.getXpForNextLevel(1)).toBe(100);
+            expect(levelingService.getXpForNextLevel(2)).toBe(282);
         });
     });
 
@@ -123,7 +123,7 @@ describe("levelingService", () => {
 
             expect(result.levelUp).toBe(true);
             expect(result.currentLevel).toBe(2);
-            expect(mockSet).toHaveBeenCalledWith({ xp: 20n, level: 2 });
+            expect(mockSet).toHaveBeenCalledWith({ xp: 120n, level: 2 });
         });
 
         it("should handle multiple level ups", async () => {