refactor(domain): move DB string conversions out of domain enums

crates/application/src/use_cases/thoughts.rs

@@ -57,11 +57,12 @@ pub async fn create_thought(
     input: CreateThoughtInput,
 ) -> Result<CreateThoughtOutput, DomainError> {
     let content = Content::new_local(input.content)?;
-    let visibility = input
-        .visibility
-        .as_deref()
-        .map(Visibility::from_db_str)
-        .unwrap_or(Visibility::Public);
+    let visibility = match input.visibility.as_deref() {
+        Some("followers") => Visibility::Followers,
+        Some("unlisted") => Visibility::Unlisted,
+        Some("direct") => Visibility::Direct,
+        _ => Visibility::Public,
+    };
     let thought = Thought::new_local(
         ThoughtId::new(),
         input.user_id,