fix(build): match project_7 proven Dockerfile — remove ENV lines + .dockerignore

project_7 docker build succeeds on competition platform.
Diff was: 5 ENV lines + .dockerignore whitelist.

ENV lines may override base image paths or trigger patch_ops.sh failures.
.dockerignore whitelist may exclude files the build needs.

Now Dockerfile is byte-identical to project_7.

.dockerignore

@@ -1,7 +0,0 @@
-# Exclude everything
-*
-
-# Only include what Dockerfile needs
-!Dockerfile
-!computility-run.yaml
-!qwen3_6_scripts/