modernize runtime, fix crashes, update deps

[polariscli]

this pr cleans up the runtime setup and fixes crashes caused by outdated loaders and dependencies.

changes

• migrated to native esm
• removed esm and dotenv in favor of node’s --env-file
• updated dependencies (express 5, node-fetch v3, eslint 9, etc.)
• replaced deprecated jade with pug
• removed unnecessary deps (fs, path)
• renamed .env to .env.example

notes

• the original api was previously crashing at runtime due to legacy esm/loader conflicts; this pr solves that
• ⚠️ replaces legacy esm loaders with native esm. older node versions and require() imports will break.
• no issues noticed during local testing, but this is a significant runtime change