feat(db): schéma MySQL cards et seed

docker/init/mysql/01-schema.sql

@@ -0,0 +1,11 @@
+CREATE TABLE IF NOT EXISTS cards (
+  id VARCHAR(36) NOT NULL,
+  question TEXT NOT NULL,
+  response TEXT NOT NULL,
+  theme VARCHAR(50) NOT NULL,
+  tags JSON,
+  createdAt DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  updatedAt DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+  PRIMARY KEY (id),
+  INDEX idx_cards_theme (theme)
+) ENGINE = InnoDB DEFAULT CHARSET = utf8mb4 COLLATE = utf8mb4_unicode_ci;