hotfix(dc/tool-c): Fix compute formula validation and binning NaN serialization

Critical fixes:
1. Compute column: Add Chinese comma support in formula validation
   - Problem: Formula with Chinese comma failed validation
   - Fix: Add Chinese comma character to allowed_chars regex
   - Example: Support formulas like 'col1（kg）+ col2，col3'

2. Binning operation: Fix NaN serialization error
   - Problem: 'Out of range float values are not JSON compliant: nan'
   - Fix: Enhanced NaN/inf handling in binning endpoint
   - Added np.inf/-np.inf replacement before JSON serialization
   - Added manual JSON serialization with NaN->null conversion

3. Enhanced all operation endpoints for consistency
   - Updated conditional, dropna endpoints with same NaN/inf handling
   - Ensures all operations return JSON-compliant data

Modified files:
- extraction_service/operations/compute.py: Add Chinese comma to regex
- extraction_service/main.py: Enhanced NaN handling in binning/conditional/dropna

Status: Hotfix complete, ready for testing

backend/prisma/migrations/20251208_add_column_mapping/migration.sql

@@ -8,3 +8,4 @@ ADD COLUMN IF NOT EXISTS "column_mapping" JSONB;
 -- 添加注释
 COMMENT ON COLUMN "dc_schema"."dc_tool_c_sessions"."column_mapping" IS '列名映射：[{originalName, safeName, displayName}] 解决特殊字符问题';
 
+