chore: release v0.3.1

[astraw]

🤖 New release

• axum-token-auth: 0.3.0 -> 0.3.1 (✓ API compatible changes)

Changelog

0.3.1 - 2026-08-15

Added

• authentication failures now emit specific diagnostic messages (Claude Opus 5)

Miscellaneous

• bump actions/checkout to v6 in the release-plz workflow (Claude Opus 4.8)

Added

• Authentication failures now emit specific diagnostic messages distinguishing no session cookie, invalid session signature, expired session, no access token, malformed token, invalid token signature, and expired access token. The ValidationErrors type carries all relevant error reasons, allowing clients to provide actionable feedback. (Claude Haiku 4.5)

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This PR was generated with release-plz.