feat: GET /tags/popular — top tags by usage count

crates/presentation/src/handlers/feed.rs

@@ -133,6 +133,20 @@ pub async fn user_thoughts_handler(
     })))
 }
 
+pub async fn get_popular_tags(
+    State(s): State<AppState>,
+    Query(params): Query<std::collections::HashMap<String, String>>,
+) -> Result<Json<serde_json::Value>, ApiError> {
+    let limit: usize = params.get("limit").and_then(|v| v.parse().ok()).unwrap_or(20);
+    let tags = s.tags.popular_tags(limit.min(100)).await?;
+    Ok(Json(serde_json::json!({
+        "tags": tags.iter().map(|(name, count)| serde_json::json!({
+            "name": name,
+            "thought_count": count,
+        })).collect::<Vec<_>>()
+    })))
+}
+
 #[utoipa::path(
     get, path = "/tags/{name}",
     params(