Enhance S3 error handling in StorageService and update .env.example documentation

- Added detailed error handling for S3 operations in StorageService to interpret and throw appropriate exceptions based on the response.
- Updated .env.example to clarify the S3 endpoint configuration for MinIO in Docker.

server/src/storage/storage.service.ts

@@ -1,6 +1,6 @@
 import { DeleteObjectCommand, GetObjectCommand, PutObjectCommand, S3Client } from '@aws-sdk/client-s3';
 import { getSignedUrl } from '@aws-sdk/s3-request-presigner';
-import { Injectable, ServiceUnavailableException } from '@nestjs/common';
+import { HttpException, Injectable, ServiceUnavailableException } from '@nestjs/common';
 import { randomUUID } from 'node:crypto';
 
 export type StoredAttachmentMeta = {
@@ -54,19 +54,27 @@ export class StorageService {
 
   async putObject(key: string, body: Buffer, contentType: string): Promise<void> {
     this.assertConfigured();
-    await this.client!.send(
-      new PutObjectCommand({
-        Bucket: this.bucket,
-        Key: key,
-        Body: body,
-        ContentType: contentType || 'application/octet-stream',
-      }),
-    );
+    try {
+      await this.client!.send(
+        new PutObjectCommand({
+          Bucket: this.bucket,
+          Key: key,
+          Body: body,
+          ContentType: contentType || 'application/octet-stream',
+        }),
+      );
+    } catch (err) {
+      throw interpretS3Failure('PutObject', err);
+    }
   }
 
   async deleteObject(key: string): Promise<void> {
     this.assertConfigured();
-    await this.client!.send(new DeleteObjectCommand({ Bucket: this.bucket, Key: key }));
+    try {
+      await this.client!.send(new DeleteObjectCommand({ Bucket: this.bucket, Key: key }));
+    } catch (err) {
+      throw interpretS3Failure('DeleteObject', err);
+    }
   }
 
   async getDownloadUrl(objectKey: string): Promise<string> {
@@ -80,8 +88,12 @@ export class StorageService {
       return `${base}/${path}`;
     }
 
-    const command = new GetObjectCommand({ Bucket: this.bucket, Key: objectKey });
-    return getSignedUrl(this.client!, command, { expiresIn: this.presignExpiresSeconds });
+    try {
+      const command = new GetObjectCommand({ Bucket: this.bucket, Key: objectKey });
+      return await getSignedUrl(this.client!, command, { expiresIn: this.presignExpiresSeconds });
+    } catch (err) {
+      throw interpretS3Failure('GetObject (presign)', err);
+    }
   }
 
   buildEquipmentObjectKey(equipmentId: string, originalName: string): string {
@@ -95,3 +107,39 @@ function sanitizeFileName(name: string): string {
   const base = name.replace(/[/\\]/g, '_').trim() || 'file';
   return base.slice(0, 200);
 }
+
+/**
+ * AWS SDK expects XML from S3-compatible APIs. A JSON/HTML 404 (e.g. wrong reverse-proxy URL)
+ * surfaces as fast-xml-parser "char '{' is not expected".
+ */
+function interpretS3Failure(operation: string, err: unknown): never {
+  if (err instanceof HttpException) {
+    throw err;
+  }
+
+  const message = err instanceof Error ? err.message : String(err);
+  const status = (err as { $metadata?: { httpStatusCode?: number } }).$metadata?.httpStatusCode;
+  const code = (err as { Code?: string; name?: string }).Code ?? (err as { name?: string }).name;
+
+  const looksLikeNonXml =
+    message.includes("char '{'") ||
+    message.includes('Deserialization error') ||
+    message.includes('fast-xml-parser');
+
+  if (looksLikeNonXml || status === 404) {
+    throw new ServiceUnavailableException(
+      `Хранилище S3/MinIO вернуло ответ не в формате S3 XML (${operation}, HTTP ${status ?? '?' }). ` +
+        'Обычно это неверный S3_ENDPOINT: укажите API MinIO внутри Docker-сети, например ' +
+        '`http://<имя-контейнера-minio>:9000` (порт S3 API), а не публичный HTTPS URL NPM, если он отдаёт JSON/HTML 404. ' +
+        'Проверьте также S3_BUCKET и что контейнер toir-light-server в одной сети с MinIO.',
+    );
+  }
+
+  if (code === 'NoSuchBucket' || message.includes('NoSuchBucket')) {
+    throw new ServiceUnavailableException(
+      `Бакет «${process.env.S3_BUCKET}» не найден в MinIO (${operation}). Создайте бакет или поправьте S3_BUCKET.`,
+    );
+  }
+
+  throw new ServiceUnavailableException(`S3 ${operation}: ${message}`);
+}