feat: complete Phase 4 combat/hunting system

- Add content migration (003_content.sql): zones, monsters, items, loot tables
- Add inventory migration (004_inventory.sql) and logs migration (006_logs.sql)
- Add Mulberry32 PRNG (src/utils/rng.js) for deterministic combat
- Add combat system (src/game/combat.js) with turn order, crit, mage bonus, 20-round cap
- Add rewards/loot system (src/game/rewards.js) and leveling (src/game/leveling.js)
- Add hunt endpoint (POST /api/hunt) with full combat flow in DB transaction
- Add hunt integration tests and unit tests for rewards/leveling/combat
- Fix session middleware to use memory store in tests (avoids cleanup hang)
- Fix huntService transaction (db.transaction() returns wrapper, must call separately)
- Add huntService to helpers.js cache invalidation for test isolation

src/middleware/session.js

@@ -5,17 +5,20 @@ const { getDb } = require('../db');
 const { AppError } = require('../utils/errors');
 
 function createSessionMiddleware() {
-  const db = getDb();
+  // Use memory store in tests to avoid session store cleanup interval hanging tests
+  const useMemoryStore = config.nodeEnv === 'test';
 
   return session({
-    store: new SessionStore({
-      client: db,
-      table: 'sessions',
-      expired: {
-        clear: true,
-        intervalMs: 900000, // 15 min cleanup
-      },
-    }),
+    store: useMemoryStore
+      ? undefined // express-session built-in memory store
+      : new SessionStore({
+          client: getDb(),
+          table: 'sessions',
+          expired: {
+            clear: true,
+            intervalMs: 900000, // 15 min cleanup
+          },
+        }),
     secret: config.sessionSecret,
     resave: false,
     saveUninitialized: false,