Error compose with spigot 1.21.9

### Describe the problem

I'm getting this error when running docker compose with spigot.

`
minecraft-server | [init] Running as uid=1000 gid=1000 with /data as 'drwxrwxrwx 1 1000 1000 4096 Oct 2 00:27 /data'
minecraft-server | [init] Image info: buildtime=2025-10-01T12:30:46.599Z,version=java21,revision=b7859d7496b66a2064c4fb75c08604a735fafab6
minecraft-server | [init] Resolving type given SPIGOT
minecraft-server | [init] Downloading Spigot from https://cdn.getbukkit.org/spigot/spigot-1.21.9.jar if missing ...
minecraft-server | [mc-image-helper] 00:40:03.697 ERROR : 'get' command failed. Version is 1.49.0
minecraft-server | me.itzg.helpers.get.RequestFailedException: Failed to download https://cdn.getbukkit.org/spigot/spigot-1.21.9.jar: status code: 404, reason phrase: Not Found
minecraft-server | at me.itzg.helpers.get.GetCommand.resolveExpectedFilename(GetCommand.java:364)
minecraft-server | at me.itzg.helpers.get.GetCommand.needsDownload(GetCommand.java:329)
minecraft-server | at me.itzg.helpers.get.GetCommand.processUrisForDirectory(GetCommand.java:303)
minecraft-server | at me.itzg.helpers.get.GetCommand.call(GetCommand.java:198)
minecraft-server | at me.itzg.helpers.get.GetCommand.call(GetCommand.java:55)
minecraft-server | at picocli.CommandLine.executeUserObject(CommandLine.java:2031)
minecraft-server | at picocli.CommandLine.access$1500(CommandLine.java:148)
minecraft-server | at picocli.CommandLine$RunLast.executeUserObjectOfLastSubcommandWithSameParent(CommandLine.java:2469)
minecraft-server | at picocli.CommandLine$RunLast.handle(CommandLine.java:2461)
minecraft-server | at picocli.CommandLine$RunLast.handle(CommandLine.java:2423)
minecraft-server | at picocli.CommandLine$AbstractParseResultHandler.execute(CommandLine.java:2277)
minecraft-server | at picocli.CommandLine$RunLast.execute(CommandLine.java:2425)
minecraft-server | at picocli.CommandLine.execute(CommandLine.java:2174)
minecraft-server | at me.itzg.helpers.McImageHelper.main(McImageHelper.java:182)
minecraft-server | Caused by: org.apache.hc.client5.http.HttpResponseException: status code: 404, reason phrase: Not Found
minecraft-server | at me.itzg.helpers.http.FilenameExtractor.extract(FilenameExtractor.java:75)
minecraft-server | at me.itzg.helpers.http.DeriveFilenameHandler.handleResponse(DeriveFilenameHandler.java:21)
minecraft-server | at me.itzg.helpers.http.DeriveFilenameHandler.handleResponse(DeriveFilenameHandler.java:10)
minecraft-server | at org.apache.hc.client5.http.impl.classic.CloseableHttpClient.execute(CloseableHttpClient.java:247)
minecraft-server | at org.apache.hc.client5.http.impl.classic.CloseableHttpClient.execute(CloseableHttpClient.java:188)
minecraft-server | at org.apache.hc.client5.http.impl.classic.CloseableHttpClient.execute(CloseableHttpClient.java:162)
minecraft-server | at me.itzg.helpers.get.GetCommand.resolveExpectedFilename(GetCommand.java:356)
minecraft-server | ... 13 common frames omitted
minecraft-server |
minecraft-server | ERROR: failed to download from https://cdn.getbukkit.org/spigot/spigot-1.21.9.jar
minecraft-server | Visit https://getbukkit.org/download/spigot to lookup the
minecraft-server | exact version or see if download site is unavailable.
minecraft-server | Click into the version entry to find the **exact** version.
minecraft-server |
minecraft-server exited with code 1`

Looks like spigot 1.21.9 is not available yet, or its given the wrong url to download.

I've downloaded and compiled the 1.21.9, but doesn't matter because when I run docker compose it try to download from `https://cdn.getbukkit.org/spigot/spigot-1.21.9.jar` instead of use the local version, wich I paste inside the server files.

If I don't set `VERSION: 1.21.9` it runs 1.21.8 by default.

Is there something else to be done?

### Container definition

```
version: '3'
services:
minecraft:
container_name: minecraft-server
image: itzg/minecraft-server
restart: 'unless-stopped'
ports:
- '25565:25565'
- '19132:19132/udp'
environment:
VERSION: '1.21.9'
EULA: 'TRUE'
DIFFICULTY: 'NORMAL'
MEMORY: '4G'
TYPE: 'SPIGOT'
volumes:
- "./data:/data"
tty: true
stdin_open: true
`

### Container logs

```
Paste logs here
````

Start with the supplied container definition, especially VERSION, TYPE, and the ./data:/data volume, then reproduce the failure with docker compose and inspect the container logs. Compare the requested Spigot version and local server jar behavior with the startup download path; done means the intended 1.21.9 setup either starts successfully or the limitation and required configuration are documented.

Written by the indexing model from the issue text.