feat: add wagon usage computation and maintenance logging features

- Implemented  utility to calculate wagon usage metrics for train schedules.
- Created  for sending wagons to maintenance with optional notes.
- Added unit tests for train builder maintenance functionalities, including formatting train run labels and building maintenance notes.
- Developed  component for merging train schedules with detailed previews and reasons for merging.
- Introduced  component for selecting wagons with search functionality and selection limits.
- Created  for displaying and filtering audit logs, including detailed views of individual log entries.
- Added  for handling API interactions related to audit logs, including fetching logs and entity types.

apps/edr-freight-api/src/modules/audit/audit.service.ts

@@ -0,0 +1,71 @@
+import { BadRequestException, Injectable, Logger } from '@nestjs/common';
+import { PaginatedResponse } from '@edr/types';
+
+import { AuditLog } from './entities/audit-log.entity';
+import { AuditLogRepository } from './audit-log.repository';
+import { AuditLogQueryDto } from './dto/audit-log-query.dto';
+import {
+  buildPaginationMeta,
+  normalizePagination,
+} from '../../common/utils/pagination.util';
+
+@Injectable()
+export class AuditService {
+  private readonly logger = new Logger(AuditService.name);
+
+  constructor(private readonly auditLogRepository: AuditLogRepository) {}
+
+  /**
+   * Persist one audit row, swallowing any failure.
+   *
+   * An audit write must never turn a successful business action into an error
+   * for the user: if this table is full, misconfigured or mid-migration,
+   * contract approvals still need to work. Failures are logged so the gap is
+   * visible in application logs rather than silent.
+   */
+  async record(entry: Partial<AuditLog>): Promise<void> {
+    try {
+      await this.auditLogRepository.record(entry);
+    } catch (error) {
+      this.logger.error(
+        `Failed to write audit log for ${entry.method} ${entry.routePath}: ${
+          error instanceof Error ? error.message : String(error)
+        }`,
+      );
+    }
+  }
+
+  /** Paginated, filtered audit history, newest first. */
+  async search(query: AuditLogQueryDto): Promise<PaginatedResponse<AuditLog>> {
+    const { page, pageSize, skip, take } = normalizePagination(query);
+
+    const from = query.from ? new Date(query.from) : undefined;
+    const to = query.to ? new Date(query.to) : undefined;
+
+    // A reversed range silently returns zero rows, which reads as "nothing
+    // happened" rather than "your filter is wrong" — reject it explicitly.
+    if (from && to && from > to) {
+      throw new BadRequestException('`from` must be earlier than `to`');
+    }
+
+    const [items, total] = await this.auditLogRepository.search({
+      type: query.type,
+      userId: query.userId,
+      method: query.method,
+      resourceId: query.resourceId,
+      isSuccess:
+        query.isSuccess === undefined ? undefined : query.isSuccess === 'true',
+      from,
+      to,
+      skip,
+      take,
+    });
+
+    return { items, meta: buildPaginationMeta(total, page, pageSize) };
+  }
+
+  /** Distinct entity types, for the filter dropdown on the audit screen. */
+  async listTypes(): Promise<string[]> {
+    return this.auditLogRepository.distinctTypes();
+  }
+}