feat: event management and websocket for updates

sparse-server/migrations/20250222071958_new_assignments.sql

@@ -0,0 +1,11 @@
+DROP TABLE beacon_category_assignment;
+
+CREATE TABLE beacon_category_assignment (
+    category_id int NOT NULL,
+    beacon_id varchar NOT NULL,
+
+    PRIMARY KEY (category_id, beacon_id),
+
+    FOREIGN KEY (category_id) REFERENCES beacon_category,
+    FOREIGN KEY (beacon_id) REFERENCES beacon_instance
+);