fix(version): read package version at runtime instead of npm env var - #5

Problem

The startup banner and the /health endpoint reported v0.1.0 instead of the real installed version whenever the proxy was started outside an npm script — e.g. node dist/proxy.js, make start, or a globally installed binary.

Root cause

src/proxy.ts and src/server.ts read process.env.npm_package_version, which is only set by npm/pnpm run scripts. In all other run modes it is undefined, so the hardcoded "0.1.0" fallback was used.

Fix

• Add src/version.ts: reads package.json located next to the module at runtime (via import.meta.url), so it resolves correctly in all run modes (tsx src/, node dist/, global binary). Falls back to the env var, then 0.0.0.
• Use getProxyVersion() in the startup banner (src/proxy.ts) and /health (src/server.ts).

Testing

• New tests/version.test.ts deletes npm_package_version to reproduce the bug and asserts the real version is returned.
• /health test now asserts version matches package.json.
• Full suite: 154/154 passing; tsc --noEmit clean.
• Manually verified node dist/proxy.js prints v0.3.0 and /health returns {"status":"ok","version":"0.3.0"}.