Add composer to Dockerfile from official composer image

[shaundrong]

Copy the latest 2.9.x build of composer to the Docker image.

[kurowski]

Suggested change

	COPY --from=composer/composer:2.9-bin /composer /usr/bin/composer
	COPY --from=composer/composer:2.9-bin /composer /usr/local/bin/composer

Looks like composer is in /usr/local instead:

myeap2 on  UP-1919-publish-portal-documentation-to-all-staff [!?] via 🐘
❯ dce -- /usr/bin/composer --version
OCI runtime exec failed: exec failed: unable to start container process: exec: "/usr/bin/composer": stat /usr/bin/composer: no such file or directory

myeap2 on  UP-1919-publish-portal-documentation-to-all-staff [!?] via 🐘
❯ dce -- /usr/local/bin/composer --version
Composer version 2.9.7 2026-04-14 13:31:52
PHP version 8.3.30 (/usr/local/bin/php)
Run the "diagnose" command to get more detailed diagnostics output.

I see we're shipping 2.9.7 and your PR bumps it to 2.9.8:

myeap2 on  UP-1919-publish-portal-documentation-to-all-staff [!?] via 🐘
✦ ❯ git diff
diff --git a/.devcontainer/docker-compose.yml b/.devcontainer/docker-compose.yml
index 240834190..dc9c26a72 100644
--- a/.devcontainer/docker-compose.yml
+++ b/.devcontainer/docker-compose.yml
@@ -1,6 +1,6 @@
 services:
   drupal:
-    image: "ghcr.io/uceap/devcontainer-drupal:main"
+    image: "ghcr.io/uceap/devcontainer-drupal:pr-47"
     volumes:
       - ../..:/workspaces:cached
   mariadb:

myeap2 on  UP-1919-publish-portal-documentation-to-all-staff [!?] via 🐘
❯ dcr -- /usr/bin/composer --version
...
Composer version 2.9.8 2026-05-13 09:28:38
PHP version 8.3.31 (/usr/local/bin/php)
Run the "diagnose" command to get more detailed diagnostics output.

Were you expecting a bigger update? Were you seeing an older version somewhere?