Release 0.6.0

[bojieli]

Version bump to 0.6.0 across all four platforms (VERSION stamped via scripts/stamp-version.sh, verified with scripts/check-version.sh) and the changelog's Unreleased section dated.

Contents of this release, all merged via #31:

• Added — in-flight and cancelled transcriptions are recorded in History with their audio; cancelled rows retry from the per-row button but are never auto-drained.
• Changed — the dictation style is now a readable, editable example box with a preview you can run (all four clients).
• Changed — Translate has its own key on the desktops; the main key is verbatim again.

Pre-tagging gates per docs/RELEASING.md: platform tests run in CI on this PR and again in the release workflow. The eval suite and the manual checks (microphone round trip etc.) have not been run for this release — to be recorded in the draft release notes.

After merge: tag v0.6.0 on the merge commit and push, which builds signed/notarized macOS and Android artifacts and opens a draft release.