fix: load CSV files from MinIO instead of local filesystem for rate search

Problem:
- CSV files uploaded to MinIO via admin panel
- But getAvailableCsvFiles() only listed local filesystem
- Result: rate search returned 0 results even though files exist in MinIO

Solution:
- Modified getAvailableCsvFiles() to check MinIO first
- Lists files from csv_rate_configs table with minioObjectKey
- Falls back to local filesystem if MinIO not configured
- Logs clearly which source is being used

This ensures rate search uses the uploaded CSV files from MinIO storage.

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

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

apps/backend/src/infrastructure/carriers/csv-loader/csv-rate-loader.adapter.ts

@@ -237,7 +237,26 @@ export class CsvRateLoaderAdapter implements CsvRateLoaderPort {
 
   async getAvailableCsvFiles(): Promise<string[]> {
     try {
-      // Ensure directory exists
+      // If MinIO/S3 is configured, list files from there
+      if (this.s3Storage && this.configService && this.csvConfigRepository) {
+        try {
+          const configs = await this.csvConfigRepository.findAll();
+          const minioFiles = configs
+            .filter(config => config.metadata?.minioObjectKey)
+            .map(config => config.metadata?.minioObjectKey as string);
+
+          if (minioFiles.length > 0) {
+            this.logger.log(`📂 Found ${minioFiles.length} CSV files in MinIO`);
+            return minioFiles;
+          } else {
+            this.logger.warn('⚠️  No CSV files configured in MinIO, falling back to local files');
+          }
+        } catch (minioError: any) {
+          this.logger.warn(`⚠️  Failed to list MinIO files: ${minioError.message}. Falling back to local files.`);
+        }
+      }
+
+      // Fallback: list from local file system
       try {
         await fs.access(this.csvDirectory);
       } catch {