fix(contribution): add @Public() to getBatchRatios endpoint for service-to-service calls

mining-service calls this endpoint without JWT token during DailySnapshot
full sync, causing 401 Unauthorized. Mark it as public since it's internal data.

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

backend/services/contribution-service/src/api/controllers/snapshot.controller.ts

@@ -7,6 +7,7 @@ import {
   BatchUserRatiosResponse,
 } from '../dto/response/snapshot.response';
 import { CreateSnapshotRequest, GetBatchRatiosRequest } from '../dto/request/snapshot.request';
+import { Public } from '../../shared/guards/jwt-auth.guard';
 
 @ApiTags('Snapshot')
 @Controller('snapshots')
@@ -71,6 +72,7 @@ export class SnapshotController {
   }
 
   @Get(':date/ratios')
+  @Public()
   @ApiOperation({ summary: '批量获取用户算力占比' })
   @ApiParam({ name: 'date', description: '快照日期 (YYYY-MM-DD)' })
   @ApiResponse({ status: 200, type: BatchUserRatiosResponse })