fix(dockerfile): parse env ports with protocol in EXPOSE

[charle-z]

Fixes the grammar side of semgrep/semgrep#11798.

Docker supports environment replacement in EXPOSE, including a valid /tcp or /udp suffix, but the extended Dockerfile grammar only allowed a numeric expose_port with protocol or a standalone expansion. This adds the missing expansion + protocol form without broadening accepted protocols.

Coverage includes $PORT/udp, ${PORT}/tcp, mixed multiple EXPOSE values, a following ENTRYPOINT, and negative cases for unsupported/empty protocol suffixes.

Validation:

• Dockerfile tree-sitter corpus: 138/138 pass
• make install: pass
• cd lang && ./test-lang dockerfile: pass
• generated C/OCaml parser builds; parser examples 2/2 pass; no undesirable Blank nodes

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