[BUG] MCQ payload index bug

[matKlju]

Bug description:
MCQ execution fails when a service contains 10+ MCQ nodes due to incorrect payload service name generation.
The GUI extracts only the last digit of the node index (e.g. 10 → 0), generating invalid payloads like:

• ..._mcq_0_x

While actual files are correctly generated as:

• ..._mcq_10_x

This mismatch causes Ruuter to call a non-existing service and return 500.

Expected behavior:
Payload service names must use the full node index:

• ..._mcq_10_x, ..._mcq_11_x, etc.
  Execution should work for 10+ MCQ nodes without errors.

Screenshots:

Current state of file system:
-rw-r--r-- 1 root root 1567 Mar 25 07:21 mcq_test.tmp
-rw-r--r-- 1 root root 1570 Mar 25 07:21 mcq_test_mcq_10_0.tmp
-rw-r--r-- 1 root root 1247 Mar 25 07:21 mcq_test_mcq_10_1.tmp
-rw-r--r-- 1 root root 1570 Mar 25 07:21 mcq_test_mcq_11_0.tmp
-rw-r--r-- 1 root root 1247 Mar 25 07:21 mcq_test_mcq_11_1.tmp
-rw-r--r-- 1 root root 1570 Mar 25 07:21 mcq_test_mcq_12_0.tmp
-rw-r--r-- 1 root root 1247 Mar 25 07:21 mcq_test_mcq_12_1.tmp
-rw-r--r-- 1 root root 1247 Mar 25 07:21 mcq_test_mcq_13_0.tmp
-rw-r--r-- 1 root root 1247 Mar 25 07:21 mcq_test_mcq_13_1.tmp
-rw-r--r-- 1 root root 1567 Mar 25 07:21 mcq_test_mcq_1_0.tmp
-rw-r--r-- 1 root root 1247 Mar 25 07:21 mcq_test_mcq_1_1.tmp
-rw-r--r-- 1 root root 1567 Mar 25 07:21 mcq_test_mcq_2_0.tmp
-rw-r--r-- 1 root root 1247 Mar 25 07:21 mcq_test_mcq_2_1.tmp
-rw-r--r-- 1 root root 1567 Mar 25 07:21 mcq_test_mcq_3_0.tmp
-rw-r--r-- 1 root root 1247 Mar 25 07:21 mcq_test_mcq_3_1.tmp
-rw-r--r-- 1 root root 1567 Mar 25 07:21 mcq_test_mcq_4_0.tmp
-rw-r--r-- 1 root root 1247 Mar 25 07:21 mcq_test_mcq_4_1.tmp
-rw-r--r-- 1 root root 1567 Mar 25 07:21 mcq_test_mcq_5_0.tmp
-rw-r--r-- 1 root root 1247 Mar 25 07:21 mcq_test_mcq_5_1.tmp
-rw-r--r-- 1 root root 1567 Mar 25 07:21 mcq_test_mcq_6_0.tmp
-rw-r--r-- 1 root root 1247 Mar 25 07:21 mcq_test_mcq_6_1.tmp
-rw-r--r-- 1 root root 1567 Mar 25 07:21 mcq_test_mcq_7_0.tmp
-rw-r--r-- 1 root root 1247 Mar 25 07:21 mcq_test_mcq_7_1.tmp
-rw-r--r-- 1 root root 1567 Mar 25 07:21 mcq_test_mcq_8_0.tmp
-rw-r--r-- 1 root root 1247 Mar 25 07:21 mcq_test_mcq_8_1.tmp
-rw-r--r-- 1 root root 1570 Mar 25 07:21 mcq_test_mcq_9_0.tmp
-rw-r--r-- 1 root root 1247 Mar 25 07:21 mcq_test_mcq_9_1.tmp

Additional information:
Service to test with:

mcq_test_2026_03_25_09_56_03.json

Probable root cause:

• Payload uses last character (label[length - 1])
• Should use full digit extraction (getLastDigits(...))