feat(action): exclude parties from target list + rep-listing party filter fix
- target-search: filter reps whose politicalParty intersects ActionGroup.excludedParties (postal/city/departement targeting; specificRepresentatives untouched per spec)
- action-detail: cherry-pick excludedParties (expand) into actionData
- helpers: normalizePartyRefs() — politicalParty is a container of {@id} refs (or array when expanded), never a string; register EVERY party in getUniqueValuesFromResource (old party[0] dropped multi- party reps and broke the listing's party filter -> 0 results)
- party option ids + filter comparisons normalize /ssr/ segment (urls differ per serving endpoint)
- verified headless: 2188 -> 1937 with parties 1+3 excluded; RN filter 131/131 on representative listing