perf(import): bypass intermediate Excel file in extraction pipeline

Replace the Extract → Write Excel → Read Excel → Import DB flow with
direct record-to-database persistence. The extractor now builds
MaterialPlanRecord[] from parsed orders and imports them without the
round-trip through a merged Excel file.

Key changes:
- Add importFromRecords() to DataImportService for record-based import
- Add SQL Server OPENJSON batch insert and atomic replace operations
  in DiscreteMaterialPlanDAO for efficient bulk writes
- Extract common import logic into private importRecords() method
- Configure explicit request/connection timeouts for SQL Server
- Add unit tests for direct record import path

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/main/services/database/sql-server.ts

@@ -38,6 +38,8 @@ export class SqlServerService implements IDatabaseService {
         user: this.config.user,
         password: this.config.password,
         database: this.config.database,
+        requestTimeout: 60000,
+        connectionTimeout: 15000,
         options: {
           encrypt: this.config.options?.encrypt ?? false,
           trustServerCertificate: this.config.options?.trustServerCertificate ?? false