[IMP] *: one Makefile to rules them all.

Create one unique generic Makefile to compile sass files.
[FIX] web,web_kanban: correct radial-gradient usage
[FIX] account_asset: moves should use the depreciation line date
[FIX] web: FieldMany2ManyBinaryMultiFiles must extend ReinitializeFieldMixin

The add attachment button should be displayed while being in edit mode, but not in view mode
As the widget depends on the form actual mode, the widget should be re-rendered each time the actual mode changes

This is the point of the ReinitializeFieldMixin class
[FIX] web: many2many_binary widget upload

once widget extended with ReinitializeFieldMixin, the event binding with the binary file input and the on_file_change method can be done in initialize_content instead of start

This fix is related to d36c8b5c9bf7ab9215bc63db6ee49bec5e5b225b
[IMP] stock: added missing 'context' parameter (opw 616952)
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