fix: update old kolaente.dev URLs to code.vikunja.io (#2342)

## Summary

- Updates all remaining `kolaente.dev` URLs in active code/config to
`code.vikunja.io`
- Updates Go Report Card badge to use current module path
`code.vikunja.io/api`
- Historical changelog references are intentionally left unchanged

Closes #655

## Files changed

- `config-raw.json` — language comment URL
- `README.md` — Go Report Card badge
- `pkg/routes/routes.go` — issue reference in comment
- `frontend/src/styles/custom-properties/colors.scss` — issue reference
in comment
- `frontend/src/helpers/time/createDateFromString.ts` — issue reference
in JSDoc
- `frontend/src/views/user/Login.vue` — issue reference in comment
- `frontend/histoire.config.ts` — PR reference in comment

---------

Co-authored-by: kolaente <k@knt.li>

README.md

@@ -5,7 +5,7 @@
 [![Install](https://img.shields.io/badge/download-v2.1.0-brightgreen.svg)](https://vikunja.io/docs/installing)
 [![Docker Pulls](https://img.shields.io/docker/pulls/vikunja/vikunja.svg)](https://hub.docker.com/r/vikunja/vikunja/)
 [![Swagger Docs](https://img.shields.io/badge/swagger-docs-brightgreen.svg)](https://try.vikunja.io/api/v1/docs)
-[![Go Report Card](https://goreportcard.com/badge/kolaente.dev/vikunja/vikunja)](https://goreportcard.com/report/kolaente.dev/vikunja/vikunja)
+[![Go Report Card](https://goreportcard.com/badge/code.vikunja.io/api)](https://goreportcard.com/report/code.vikunja.io/api)
 
 # Vikunja
 

config-raw.json

@@ -938,7 +938,7 @@
                 {
                     "key": "language",
                     "default_value": "\u003cunset\u003e",
-                    "comment": "The language of the user interface. Must be an ISO 639-1 language code followed by an ISO 3166-1 alpha-2 country code. Check https://kolaente.dev/vikunja/vikunja/frontend/src/branch/main/src/i18n/lang for a list of possible languages. Will default to the browser language the user uses when signing up."
+                    "comment": "The language of the user interface. Must be an ISO 639-1 language code followed by an ISO 3166-1 alpha-2 country code. Check https://code.vikunja.io/vikunja/tree/main/frontend/src/i18n/lang for a list of possible languages. Will default to the browser language the user uses when signing up."
                 },
                 {
                     "key": "timezone",