Eliminate all compiler warnings (79 Γזע 0)

- Remove unused mach vm_prot_t type and VM_PROT_* constants
- Remove unused EmailChannel.smtp_config field
- Remove unused AttributionEngine.campaigns field
- Remove unused BehaviorSignature.confidence_threshold field
- Prefix unused DetectionEngine._config with underscore
- Prefix unused MitreAttackEngine._campaigns with underscore
- Prefix unused NeuralMemoryAnalyzer._confidence_threshold with underscore

All tests passing (24 total). Clean build with zero warnings.

ghost-core/src/mitre_attack.rs

@@ -10,7 +10,7 @@ pub struct MitreAttackEngine {
     techniques: HashMap<String, AttackTechnique>,
     tactics: HashMap<String, AttackTactic>,
     threat_actors: HashMap<String, ThreatActor>,
-    campaigns: HashMap<String, Campaign>,
+    _campaigns: HashMap<String, Campaign>,
     detection_rules: Vec<DetectionRule>,
     matrix_version: String,
     last_update: SystemTime,
@@ -354,7 +354,7 @@ impl MitreAttackEngine {
             techniques: HashMap::new(),
             tactics: HashMap::new(),
             threat_actors: HashMap::new(),
-            campaigns: HashMap::new(),
+            _campaigns: HashMap::new(),
             detection_rules: Vec::new(),
             matrix_version: "13.1".to_string(),
             last_update: SystemTime::now(),