fix: Ensure to uses REAL for Decimal values

[BobdenOs]

Currently when using cds.Decimal values on SQLite it results in the table using NUMERIC as the column type. This type is very similar to the javascript Number type, but with one primary difference that it behaves based upon the native type of the value.

// javascript
1   / 2   // 0.5
1.0 / 2.0 // 0.5
1n  / 2n  // 0n

// C/C++
1   / 2   // 0
1.0 / 2.0 // 0.5

So SQLite has the same behavior as C, but with the dynamic typing of javascript resulting in inconsistent and unpredictable behaviors. By explicitly defining Decimal as a REAL it will behave consistently as the floating number that it is supposed to be.