feat: add license migration file

backend/migration/000015_create_license_table.down.sql

@@ -0,0 +1,2 @@
+-- Drop license table
+DROP TABLE IF EXISTS license;

backend/migration/000015_create_license_table.up.sql

@@ -0,0 +1,13 @@
+-- Create license table
+CREATE TABLE IF NOT EXISTS license (
+    id SERIAL PRIMARY KEY,
+    type VARCHAR(10) NOT NULL,
+    data BYTEA,
+    code VARCHAR(255),
+    created_at TIMESTAMPTZ DEFAULT CURRENT_TIMESTAMP
+);
+
+-- Create indexes
+CREATE INDEX IF NOT EXISTS idx_license_type ON license (type);
+CREATE INDEX IF NOT EXISTS idx_license_code ON license (code);
+CREATE INDEX IF NOT EXISTS idx_license_created_at ON license (created_at);