SQLHelperFunctions — wrong Format masks in toISO

SQLHelperFunctions: correct toISO Format masks (mm vs nn)
- Component: `src/Modules/SQLHelperFunctions.bas` (top)

### Problem
- Uses month/minute masks incorrectly; minutes display as month.

### Snippet (actual)
```vb
Public Function toISO(dt) As String
toISO = Format(dt, "YYYY-MM-DD") & "T" & Format(dt, "HH:MM:SS")
End Function
```

### Expected
```vb
Public Function toISO(dt) As String
toISO = Format(dt, "yyyy-mm-dd") & "T" & Format(dt, "hh:nn:ss")
End Function
```

### Steps to Reproduce
1) Print `toISO(Now)` and compare minutes field.

### Actual
- Minutes are incorrect.

### Proposed Fix
- Use `mm` for month and `nn` for minutes.

---

打开 src/Modules/SQLHelperFunctions.bas 并检查顶部的 toISO 函数。使用 Print toISO(Now) 重现该问题，然后验证输出中的月份字段和分钟字段是否使用了预期的掩码，并与 ISO 风格的输出一致。

由索引模型根据 Issue 内容生成。