fix(timezone): use UTC for database storage and local time for UI display

Backend changes:
- SQL Server dialect: GETDATE() → SYSUTCDATETIME()
- MySQL dialect: NOW() → UTC_TIMESTAMP()
- Ensures OperationTime and EndTime use consistent UTC timezone

Frontend changes:
- formatDateTime: display UTC timestamps in user's local timezone
- Uses getFullYear/getMonth/getDate/getHours (local) instead of UTC methods

Data migration:
- Executed migration script to fix historical OperationTime records
- All existing records now have correct UTC timestamps
- Execution duration now accurate (minutes, not hours)

Impact:
- New executions store UTC timestamps correctly
- UI displays times in user's local timezone (UTC+8 for CN users)
- Historical data corrected via migration
- Time difference between OperationTime and EndTime now accurate

src/main/services/database/dialects/mysql-dialect.ts

@@ -27,7 +27,7 @@ export class MySqlDialect implements SqlDialect {
   }
 
   currentTimestamp(): string {
-    return 'NOW()'
+    return 'UTC_TIMESTAMP()'
   }
 
   upsert(params: {

src/main/services/database/dialects/sqlserver-dialect.ts

@@ -26,7 +26,7 @@ export class SqlServerDialect implements SqlDialect {
   }
 
   currentTimestamp(): string {
-    return 'GETDATE()'
+    return 'SYSUTCDATETIME()'
   }
 
   upsert(params: {