_generateFormState._computeItemsHash included item.value for
switches and dropdowns (only text fields were excluded). On the
add-app page, _buildSourceSpecificForm mutates item.value from
additionalSettings on every rebuild, so any value change via a
related onValueChanges callback would alter the hash, trigger
_initFormData, dispose all TextEditingControllers, and kill the
keyboard.
Hash now uses only key + runtime type for all item kinds -- form
re-initialization is driven by widget key changes (source
switch), not value fluctuations.
