The EventCard logic assume interestedIds not being present means the
account can't set events as interested. Fix this logic by checking if
the account is valid instead and always have interestedIds present on
the account store.
Some functions in luxon default to the system's locale while other
functions default to "en-US". Explicitly set the locale everywhere
the luxon objects are created to avoid possible mismatches and
unexpected behaviour should the system's locale be different.
Replace the convoluted useAccountSession composable with a pinia store
that in addition allows for the consolidation of all session related
functions to grouped into one module.
