Add package license metadata

[yanziwei]

Summary

• add MIT license metadata to the published package manifests
• include a patch changeset for @naverpay/prometheus-core, @naverpay/prometheus-hono, @naverpay/prometheus-koa, and @naverpay/prometheus-next
• align package metadata with the repository's existing MIT LICENSE file

Verification

• npm view @naverpay/prometheus-{core,hono,koa,next}@latest license --json returned empty output
• local manifest assertion confirmed license: MIT for all four package manifests
• git diff --check
• npm pack --dry-run --ignore-scripts --json passed for packages/hono, packages/koa, and packages/next

Note: npm pack for packages/core is blocked by the existing dependency key vm2<3.9.17, which npm reports as an invalid tag name. This PR does not change dependencies.