The 'Link de import' button was disabled whenever no agenda filter was
active, forcing a filter to subscribe to the full campaign agenda. The
server already supported the empty-filter case (filterMunicipality empty
= entire creator scope via buildFeedWhere/resolveFeedCreatorAccess), so
this unlocks the button and drops the now-dead state/hasFilters props.
The dialog copy is neutralized ('recorte' -> 'agenda') to cover both the
filtered and filterless shapes.
Int tests pin the content acceptance: coordinator filterless feed covers
all municipalities; advisor filterless feed is scoped to the administered
portfolio (nothing out-of-scope leaks); an advisor with no assigned
municipality serves an empty feed (fail-closed). A new component test
asserts the button is enabled with zero filters and the create flow works.
Closes#437
