fix: handle plain month number in attendance route, not just YYYY-MM

AttendanceAdmin sends ?year=YYYY&month=M (separate params), but the
route handler assumed month was always in "YYYY-MM" format. When
query.month was just "4", the split produced NaN for month and 4 for
year, causing the service to skip the month filter entirely.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "app-ts",
-  "version": "1.6.0",
+  "version": "1.6.1",
   "description": "",
   "main": "dist/server.js",
   "scripts": {