refactor: reorganize and dedupe message catalog
dissolve the namespace-artifact files (view.action/label/empty) and the
misc aggregation files (components/screens/view.misc) into feature-named
files, so every key's prefix matches its filename. relocate or rename the
contained keys to their feature home, splitting out 14 new per-component
and per-screen files. merge duplicate and near-duplicate strings onto a
single key (generic errors, audience-option labels, casing/apostrophe
drift, etc.). the three large files (composer, messages, settings) are
deliberately kept whole.
paraglide:compile and typecheck pass.