Quality slightly drops with each operation

Crop and rotate operations cause quality to slightly drop and this effect accumulates.
Both of these operations must just accumulate some matrix transformation without actual render (except preview).

Rendering must happen only during saving into a file. During this final rendering, all operations must be applied at once if possible. It might be difficult to "sandwich" operations without loss of quality, e.g. `crop, rotate, crop`. But if possible to represent such a heterogeneous sequence of operations as a single matrix transformation, that would be perfect.

Sequences like `crop, crop, crop` or `rotate, rotate, rotate` always can be reduced to a single operation.

**Example 1** (original image is `100x100`):
```
crop(10,10,20,20)
crop(5,5,10,10)
```
is the same as
```
crop(15,15,20,20)
```

**Example 2**:
```
rotate(90 degrees)
rotate(-10 degrees)
rotate(40 degrees)
rotate(-20 degrees)
```
is the same as
```
rotate(100 degrees)
```

Start by tracing where crop and rotate operations are applied, how preview rendering differs from saving, and where the final image is rendered. Compare repeated crop and rotate sequences with their equivalent combined transformations, then verify that saving applies the operations together without cumulative quality loss.

Written by the indexing model from the issue text.