SQLSelect — LeftJoin/RightJoin ByRef type mismatch

SQLSelect: type LeftJoin/RightJoin params as String
- Component: `src/ClassModules/SQLSelect.cls` (around 120–143)

### Problem
- Untyped parameters (`Variant` ByRef) cause mismatches when passed into `AddJoin`.

### Snippet (actual)
```vb
Public Sub LeftJoin(sTable, sAlias, Optional sCondition As String = "")
AddJoin "LEFT OUTER", sTable, sAlias, sCondition
End Sub

Public Sub RightJoin(sTable, sAlias, Optional sCondition As String = "")
AddJoin "RIGHT OUTER", sTable, sAlias, sCondition
End Sub
```

### Expected
```vb
Public Sub LeftJoin(sTable As String, sAlias As String, Optional sCondition As String = "")
AddJoin "LEFT OUTER", sTable, sAlias, sCondition
End Sub

Public Sub RightJoin(sTable As String, sAlias As String, Optional sCondition As String = "")
AddJoin "RIGHT OUTER", sTable, sAlias, sCondition
End Sub
```

### Steps to Reproduce
1) Call `LeftJoin`/`RightJoin` with string literals under strict compilation.

### Actual
- Compile-time "ByRef argument type mismatch" in some contexts.

### Proposed Fix
- Type parameters as `String`.

---

打开 src/ClassModules/SQLSelect.cls 的第 120–143 行附近，检查 LeftJoin 和 RightJoin 的声明及其对 AddJoin 的调用。使用字符串字面量编译或重现严格编译场景；完成标准是两个方法都能在没有 ByRef 参数类型不匹配错误的情况下编译通过。

由索引模型根据 Issue 内容生成。