* chore: migrate from zod/v3 to zod/v4
This commit contains the logic changes
* chore: migrate imports from zod/v3 to zod/v4
This contains import updates and adds explicit record keys as zod/v4 requires these now
* ci: enforce usage of zod/v4
* feat(datasource): add elm-package datasource
* refactor(elm): inline test fixtures
* fix(elm): correct import ordering in test file
* fix(elm): use zod/v3 import to match codebase conventions
* refactor(elm): rename types.ts to schema.ts
Follow project convention of using schema.ts for zod schema files.
* test(elm): add test for invalid JSON response
Use v8 ignore if directive and add test covering the null result
path when the API returns invalid JSON.
* refactor(elm): remove unreachable null check
* test(elm): add test for default registry URL fallback
* refactor(elm): guard against missing registryUrl instead of fallback
* fix(elm): handle ZodError gracefully instead of throwing
* feat(elm): add package cache for elm-package datasource
Sebastian Poxhofer