refactor: SocialActor rich queries, migrate remaining handlers, slim SocialQueryPort

SocialQuery returns SocialActor (identity+handle+display_name+avatar_url)
instead of bare SocialIdentity. Migrated get_following_page,
get_followers_page, get_blocked_actors_page to use cases. Moved
get_activity_feed + get_profile from SocialQueryPort to SocialQuery.
Legacy SocialQueryPort remains only for get_users listing.

crates/application/src/social/get_blocked.rs

@@ -1,11 +1,11 @@
-use domain::{errors::DomainError, value_objects::{SocialIdentity, UserId}};
+use domain::{errors::DomainError, value_objects::{SocialActor, UserId}};
 
 use super::{deps::SocialQueryDeps, queries::GetBlockedQuery};
 
 pub async fn execute(
     deps: &SocialQueryDeps,
     query: GetBlockedQuery,
-) -> Result<Vec<SocialIdentity>, DomainError> {
+) -> Result<Vec<SocialActor>, DomainError> {
     let user_id = UserId::from_uuid(query.user_id);
     deps.social_query.get_blocked(&user_id).await
 }