update flash card, test

supabase/create/update.sql

@@ -0,0 +1,7 @@
+CREATE TABLE test_category (
+                               id    SERIAL PRIMARY KEY,
+                               name  VARCHAR(100) NOT NULL,  -- "TOEIC", "IELTS Academic", "HSK 1"...
+                               slug  VARCHAR(100) UNIQUE     -- "toeic", "ielts", "hsk-1"
+);
+
+ALTER TABLE test ADD COLUMN category_id INT REFERENCES test_category(id);