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`.

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