add migration

ts/database/migrations/base-migration.ts

@@ -0,0 +1,22 @@
+/**
+ * Abstract base class for database migrations.
+ * All migrations must extend this class and implement the abstract members.
+ */
+
+import type { TQueryFunction } from '../types.ts';
+
+export abstract class BaseMigration {
+  /** The migration version number (must be unique and sequential) */
+  abstract readonly version: number;
+
+  /** A short description of what this migration does */
+  abstract readonly description: string;
+
+  /** Execute the migration's SQL statements */
+  abstract up(query: TQueryFunction): void;
+
+  /** Returns a human-readable name for logging */
+  getName(): string {
+    return `Migration ${this.version}: ${this.description}`;
+  }
+}