Bump version to 0.18.1

[Xuanwo]

This PR will bump reqsign version to 0.18.1

All other crates bumped to 2.0.1

Summary

• Enabled reqsign-http-send-reqwest and reqsign-file-read-tokio to build on WASM, tightening cross-platform coverage.
• Improved credential handling by returning credential_invalid when no credential is available and trimming/encoding AWS
  tokens correctly.
• Aligned internal crate versions for the 0.18.1/2.0.1 release and fixed the release workflow.

Commits

• bd9eee5 Bump version to 0.18.1
• 4997eef feat: Make http-send-reqwest available on wasm (feat: Make http-send-reqwest available on wasm #656)
• 125362c feat: Return credential_invalid while no credential found (feat: Return credential_invalid while no credential found #655)
• c7953e5 feat(context-file-read-tokio): Allow file read tokio been built on wasm (feat(context-file-read-tokio): Allow file read tokio been built on wasm #654)
• 1744efc fix(services-aws-v4): Ensure token has been trimmed and encoded (fix(services-aws-v4): Ensure token has been trimmed and encoded #653)
• 60d1ca9 ci: fix up release workflow (ci: fix up release workflow #650)

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This PR was primarily authored with Codex using GPT-5-Codex and then hand-reviewed by me. I AM responsible for every change made in this PR. I aimed to keep it aligned with our goals, though I may have missed minor issues. Please flag anything that feels off, I'll fix it quickly.

[tisonkun]

@Xuanwo Any summary of the changeset?

[Xuanwo]

@Xuanwo Any summary of the changeset?

Updated in PR desc.