Extended Issue #891 fix to cover manual node addition via the UI:
1. HandleAddNode now checks for duplicates by Host URL (not name)
2. Disambiguator applied to PVE, PBS, and PMG node creation
3. Error message updated: 'host URL already exists' instead of 'name already exists'
This ensures the fix works whether nodes are added via:
- Agent auto-registration ✓
- Manual UI setup ✓
All node creation paths now consistently:
- Match by Host URL only
- Disambiguate duplicate hostnames with IP: 'px1' → 'px1 (10.0.2.224)'
rcourtman
de448dade6