FRE-4510: Implement feature flag checks for spam classification

- Create centralized feature flag management system (feature-flags.ts)
- Add 15 feature flags across SpamShield, VoicePrint, and Platform categories
- Update spamshield.config.ts to use checkFlag() for all flags
- Add feature flag checks to all spamshield.service.ts methods:
  * NumberReputationService.checkReputation()
  * NumberReputationService.checkMultiSource()
  * SMSClassifierService.classify()
  * CallAnalysisService.analyzeCall()
  * SpamFeedbackService.recordFeedback()
- Update index.ts exports to include feature flag utilities
- Flags support runtime updates via FLAG_<KEY> environment variables

Flags implemented:
- SpamShield: enableNumberReputation, enableContentClassification,
  enableBehavioralAnalysis, enableCommunityIntelligence,
  enableRealTimeBlocking, enableMultipleSources, enableMLClassifier
- VoicePrint: enableMLService, enableFAISSIndex, enableBatchAnalysis,
  enableRealtimeAnalysis, enableMockModel
- Platform: enableAuditLogs, enableKPITracking

apps/api/src/services/voiceprint/index.ts

@@ -8,8 +8,12 @@ export {
   audioPreprocessingConfig,
   voicePrintFeatureFlags,
   voicePrintRateLimits,
+  checkFlag,
+  isFeatureEnabled,
 } from './voiceprint.config';
 
+
+
 // Services
 export {
   AudioPreprocessor,

apps/api/src/services/voiceprint/voiceprint.config.ts

@@ -72,13 +72,13 @@ export const audioPreprocessingConfig = {
   maxSilenceDurationMs: 500,
 };
 
-// Feature flags
+// Feature flags - use centralized system
 export const voicePrintFeatureFlags = {
-  enableMLService: false,
-  enableFAISSIndex: true,
-  enableBatchAnalysis: true,
-  enableRealtimeAnalysis: false,
-  enableMockModel: true,
+  enableMLService: checkFlag('voiceprint.enable.ml.service', false),
+  enableFAISSIndex: checkFlag('voiceprint.enable.faiss.index', true),
+  enableBatchAnalysis: checkFlag('voiceprint.enable.batch.analysis', true),
+  enableRealtimeAnalysis: checkFlag('voiceprint.enable.realtime.analysis', false),
+  enableMockModel: checkFlag('voiceprint.enable.mock.model', true),
 };
 
 // Rate limits for voice analysis