feat(domain): SearchPort trait with thought and user search

crates/domain/src/ports.rs

@@ -136,3 +136,21 @@ pub trait FeedRepository: Send + Sync {
     async fn public_feed(&self, page: &PageParams, viewer_id: Option<&UserId>) -> Result<Paginated<FeedEntry>, DomainError>;
     async fn search(&self, query: &str, page: &PageParams, viewer_id: Option<&UserId>) -> Result<Paginated<FeedEntry>, DomainError>;
 }
+
+#[async_trait]
+pub trait SearchPort: Send + Sync {
+    /// Full-text search over public thoughts, ranked by trigram similarity.
+    async fn search_thoughts(
+        &self,
+        query: &str,
+        page: &PageParams,
+        viewer_id: Option<&UserId>,
+    ) -> Result<Paginated<FeedEntry>, DomainError>;
+
+    /// Search users by username or display_name, ranked by trigram similarity.
+    async fn search_users(
+        &self,
+        query: &str,
+        page: &PageParams,
+    ) -> Result<Paginated<User>, DomainError>;
+}