fix(docker): normalize CRLF line endings on Windows checkouts (#951)

A Windows Git checkout with checkout-time CRLF conversion enabled
produces CRLF working-tree copies of package.json and
scripts/rocm-entrypoint.sh, breaking the Docker build two ways:

- The frontend stage's `sed -i -z 's/,\n  ]/…/'` is LF-anchored, so
  it doesn't match against \r\n and leaves an invalid trailing comma
  in package.json, which then fails JSON parsing in the vite build.
- The final stage copies rocm-entrypoint.sh straight from the build
  context; with a CRLF shebang the container reports the misleading
  "no such file or directory" for an entrypoint that plainly exists,
  because Linux can't resolve "/bin/sh\r" as an interpreter.

Add .gitattributes forcing LF for both files at checkout time, plus a
sed normalization step in each Dockerfile stage for resilience with
clones that predate the .gitattributes rule.

Fixes #915

.gitattributes

@@ -0,0 +1,2 @@
+package.json text eol=lf
+scripts/*.sh text eol=lf