fix(auth): normalize default resource URL ports

[DebadityaHait]

Summary

• Normalize explicit HTTP port 80 and HTTPS port 443 when canonicalizing resource URLs.
• Preserve non-default ports, existing URL components, and authority edge cases.

Fixes #3297

Testing

• uv run --frozen pytest tests/shared/test_auth_utils.py (19 passed)
• uv run --frozen pyright src/mcp/shared/auth_utils.py tests/shared/test_auth_utils.py (0 errors)
• uv run --frozen ruff check .
• uv run --frozen ruff format --check .
• Full coverage/matrix checks delegated to CI because the local Windows environment has no Bash; bash scripts/test could not run.

AI assistance

AI assistance was used during investigation and implementation. I reviewed the change, reproduced the issue, and understand the code and tests being submitted.

[cubic-dev-ai]

All reported issues were addressed across 2 files

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[github-actions]

Thanks for the contribution. This repository only keeps pull requests open when they're linked to an issue that a maintainer has assigned to the author — CONTRIBUTING.md explains why and how we work. This PR has been closed for now because you aren't currently assigned to #3297.

If a maintainer would like this change as a PR from you, they'll assign you to #3297 and this PR will reopen automatically — there's nothing more you need to do. (If you opened the issue, this PR already shows up on its timeline.)

There's no need to open a new PR — this one will be reopened. While it's closed, please push any updates as new commits rather than force-pushing, since GitHub can't reopen a PR whose branch has been rewritten.

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