UI: Fix VNF NIC mapping network select always disabled

[Gia-Bursulaia]

Description

Fixes VNF NIC mapping network select dropdown which was permanently disabled in the UI.

Root cause:
In ui/src/views/compute/wizard/VnfNicsSelection.vue the disabled attribute
was written as a plain HTML string instead of a Vue reactive binding (missing : prefix).
In Vue/Ant Design, any non-empty string is treated as truthy, making the select
always disabled regardless of state.

Steps to reproduce:

1. Create an Isolated network (WAN) and L2 network (LAN)
2. Go to Network → VNF Appliances → Add VNF Appliance
3. Select a VNF template with NIC definitions
4. Add networks on the Networks step
5. Proceed to VNF NIC Mappings step — all dropdowns are disabled

Expected: Network dropdowns are enabled and selectable
Actual: All dropdowns permanently disabled, VNF cannot be deployed via UI

Tested on: CloudStack 4.22.1.0, KVM hypervisor

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Feature/Enhancement Scale or Bug Severity

• Minor

[boring-cyborg]

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[bernardodemarco]

@blueorangutan ui

[blueorangutan]

@bernardodemarco a Jenkins job has been kicked to build UI QA env. I'll keep you posted as I make progress.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 18.10%. Comparing base (be51948) to head (0b25837).
⚠️ Report is 15 commits behind head on main.

Additional details and impacted files

@@ Coverage Diff @@## main #13359 +/- ##
=========================================
Coverage 18.10% 18.10% - Complexity 16750 16751 +1 
=========================================
Files 6037 6037 Lines 542798 542798 Branches 66457 66457 =========================================
Hits 98298 98298 - Misses 433453 433455 +2 + Partials 11047 11045 -2 

Flag	Coverage Δ
uitests	3.51% <ø> (ø)
unittests	19.27% <ø> (ø)

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[weizhouapache]

closing in favor of #13423