feat: enhance build process and Dockerfiles for improved artifact handling and dependency resolution

Signed-off-by: d9pouces <github@19pouces.net>

tests/configs/Java.yaml.j2

@@ -18,5 +18,20 @@ configurations:
     repositories: []
   java:
     repositories:
+    # First entry: named "central" so Maven's mirrorOf=* (built on
+    # repositories[0]) redirects everything here without invalidating the
+    # maven-dependency-plugin already cached under that repository id
+    # during the Dockerfile's warm-up step. All other tools just see it as
+    # an ordinary repository, and find the test artifact here.
     - name: central
       url: https://host.docker.internal:{{ 'JAVA_REPO_PORT' | env }}/
+    # Second entry: only SBT needs this. With
+    # -Dsbt.override.build.repos=true (the only way SBT actually consults
+    # this file for project dependencies, not just its own bootstrap), the
+    # repositories listed here become the *only* ones available - without a
+    # real Maven Central mirror among them, SBT can't resolve scala-library
+    # itself. Maven ignores it (mirrorOf=* already redirects everything to
+    # the first entry); Gradle/Ivy/Leiningen just see one more unused
+    # resolver, since the test artifact is already found via "central".
+    - name: maven-central-fallback
+      url: https://repo1.maven.org/maven2/