feat: add alpine-3.24 build config (#5)

## Summary

Adds an `alpine-3.24` build configuration, mirroring the existing `alpine-3.23` setup.

- `builder/Dockerfile.alpine-324` — `FROM alpine:3.24`, `OS_IDENTIFIER=alpine-324`, copies `package.alpine-324`
- `builder/package.alpine-324` — nfpm spec (identical to 323)
- `builder/docker-compose.yml` — new `alpine-324` service
- `Makefile` `PLATFORMS` and `Justfile` `build-r-alpine-324` target
- `.crow/build.yaml` — alpine-324 matrix entries (arm64 + amd64), newest-first

Existing alpine-322/323 matrix entries are left intact.

Reviewed-on: #5

Makefile

@@ -1,4 +1,4 @@
-PLATFORMS := ubuntu-2004 ubuntu-2204 ubuntu-2404 ubuntu-2604 debian-10 debian-11 debian-12 centos-7 centos-8 rhel-9 opensuse-155 fedora-38 fedora-39 fedora-40 alpine-321 alpine-322 alpine-323 rhel-10
+PLATFORMS := ubuntu-2004 ubuntu-2204 ubuntu-2404 ubuntu-2604 debian-10 debian-11 debian-12 centos-7 centos-8 rhel-9 opensuse-155 fedora-38 fedora-39 fedora-40 alpine-321 alpine-322 alpine-323 alpine-324 rhel-10
 SLS_BINARY ?= ./node_modules/serverless/bin/serverless.js
 
 deps: