npm: version lookup returns 502

[kokes]

Looking up a version (latest or e.g. 4.18.1) returns a 502, because it mistreats the slash in lodash/latest as a namespace separator and escapes it.

$ curl -i http://localhost:8080/npm/lodash/latest
HTTP/1.1 502 Bad Gateway
Content-Type: application/json
X-Request-Id: mbp.local/Z9um7GRQhM-000001
Date: Thu, 08 Oct 2026 11:09:00 GMT
Content-Length: 41

{"error":"failed to fetch from upstream"}

With this PR in place:

$ curl -i http://localhost:8080/npm/lodash/latest
HTTP/1.1 200 OK
Content-Type: application/json
X-Request-Id: mbp.local/OOnSt03Chy-000001
Date: Thu, 08 Oct 2026 11:10:06 GMT
Content-Length: 1668

{"bugs":{"url":"https://github.com/lodash/lodash/issues"},"dist":{"shasum":"ff2b66c1f6326d59513de2407bf881439812771c","tarball":"http://localhost:8080/npm/lodash/-/lodash-4.18.1.tgz","fileCount":1051,"integrity":"sha512-dMInicTPVE8d1e5otfwmmjlxkZoUpiVLwyeTdUsi/Caj/gfzzblBcCE5sRHV/AsjuCmxWrte2TNGSYuCeCq+0Q==","signatures":[{"sig":"MEUCIQDZo+W4JJ5T/9RkS8Wz1uN7Gw+CBvP16yGeT8H9lnb+sAIgKM5Nqj636zyRL2YOUuhbSK2e1DhK2VBaMXiVNIYMq1M=","keyid":"SHA256:DhQ8wR5APBvFHLF/+Tc+AYvPOdTpcIDqOhxsBHRwC7U"}],"unpackedSize":1413741},"icon":"https://lodash.com/icon.svg","main":"lodash.js","name":"lodash","author":{"name":"John-David Dalton","email":"john.david.dalton@gmail.com"},"gitHead":"4f0b76e2eca13de1c1fe8b4305abc1f7d63f4b86","license":"MIT","scripts":{"test":"echo \"See https://travis-ci.org/lodash-archive/lodash-cli for testing details.\""},"_npmUser":{"name":"jdalton","email":"john.david.dalton@gmail.com"},"homepage":"https://lodash.com/","keywords":["modules","stdlib","util"],"repository":{"url":"git+https://github.com/lodash/lodash.git","type":"git"},"_npmVersion":"10.9.4","description":"Lodash modular utilities.","directories":{},"maintainers":[{"name":"mathias","email":"mathias@qiwi.be"},{"name":"jdalton","email":"john.david.dalton@gmail.com"},{"name":"bnjmnt4n","email":"benjamin@dev.ofcr.se"}],"_nodeVersion":"22.21.1","contributors":[{"name":"John-David Dalton","email":"john.david.dalton@gmail.com"},{"name":"Mathias Bynens","email":"mathias@qiwi.be"}],"_hasShrinkwrap":false,"_npmOperationalInternal":{"tmp":"tmp/lodash_4.18.1_1775077280191_0.6534118914634555","host":"s3://npm-registry-packages-npm-production"},"_id":"lodash@4.18.1","version":"4.18.1"}