FRE-5006: VoicePrint quality improvements

- P2-1: Consolidate mock ML logic to Python canonical source
- P2-2: Fix weak hashes with SHA-256
- P2-3: Parallelize batch processing with Promise.allSettled()
- P2-4: Add DI pattern support to services
- P2-5: Add structured logging utility
- P3-2: Persist batch jobId for result retrieval

Co-Authored-By: Paperclip <noreply@paperclip.ing>

services/voiceprint/src/voiceprint.service.ts

@@ -8,6 +8,7 @@ import {
   voicePrintFeatureFlags,
 } from './voiceprint.config';
 import { checkFlag } from './voiceprint.feature-flags';
+import { createHash } from 'crypto';
 
 // Audio preprocessing service
 export class AudioPreprocessor {
@@ -197,12 +198,10 @@ export class VoiceEnrollmentService {
   }
 
   private computeEmbeddingHash(embedding: number[]): string {
-    let hash = 0;
-    for (let i = 0; i < embedding.length; i++) {
-      hash = ((hash << 5) - hash) + embedding[i];
-      hash |= 0;
-    }
-    return `vp_${Math.abs(hash).toString(16)}_${embedding.length}`;
+    const hash = createHash('sha256')
+      .update(JSON.stringify(embedding))
+      .digest('hex');
+    return `vp_${hash.substring(0, 16)}_${embedding.length}`;
   }
 }
 
@@ -287,13 +286,10 @@ export class AnalysisService {
   }
 
   private computeAudioHash(buffer: Buffer): string {
-    let hash = 0;
-    const sampleSize = Math.min(buffer.length, 1024);
-    for (let i = 0; i < sampleSize; i += 8) {
-      hash = ((hash << 5) - hash) + buffer.readUInt8(i);
-      hash |= 0;
-    }
-    return `audio_${Math.abs(hash).toString(16)}`;
+    const hash = createHash('sha256')
+      .update(buffer)
+      .digest('hex');
+    return `audio_${hash.substring(0, 16)}`;
   }
 }