Fix: Detect "unknown" string as incomplete configuration

Extended incomplete configuration check to handle configs that have
literal "unknown" string values (not just empty strings).

This handles cases where config migration or incomplete setup left
placeholder "unknown" values in PBS_SERVER or PBS_DATASTORE fields.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

pbs-client-installer.sh

@@ -168,7 +168,8 @@ show_targets_list() {
             echo "Target: $target"
 
             # Check if config seems incomplete
-            if [ -z "$PBS_SERVER" ] || [ -z "$PBS_DATASTORE" ]; then
+            if [ -z "$PBS_SERVER" ] || [ -z "$PBS_DATASTORE" ] || \
+               [ "$PBS_SERVER" = "unknown" ] || [ "$PBS_DATASTORE" = "unknown" ]; then
                 echo "  Status: ⚠ Incomplete configuration"
                 echo "  Action: Use option 3 (Edit target) to reconfigure"
             else