Hi there,
Hope you don't mind me bidding over the budget, I feel this is the minimum that would be fair for developing something like this.
I imagine the web app as follows:
1) have 2 modes, edit mode and preview mode. In edit mode all images (or parts of them if cropped) would have a bonding box around them, and could be selected in order to be rotated or moved. In preview mode no bounding boxes would be shown and all the editing tools would be disabled
2) crop tool - this is the heaviest to implement, I didn't factor cropping using bezier shapes but rather a polygon tool - click to define the first point, every subsequent click defines a new point and a line is connected from the previous point to the new point. Clicking on the starting point again would close the shape and perform the clipping and updating the bouding box
3) move tool, click on the tool and then click the image (or part of image) to be moved, moving starts and as the mouse moves the selected object/image moves. Clicking again stops the moving.
4) rotate tool, click the tool and then click the object/image to be rotated. As the mouse moves, the object rotates. Clicking stops the rotation.
5) upload image allows adding a new image/object. Image would be added in the center of the canvas.
Regards,
Julijan