MoveBit 0.0.7

Release-qualification build. There are no product behaviour changes since
0.0.6: this release exists so the fixed signed-AppImage updater can be
exercised across a real published pair (0.0.6 → 0.0.7) on x64 and arm64,
including a full GUI relaunch with persisted data and an executed
rollback/rejected-downgrade pass.

Fixed

• Linux placement acceptance waits for the previous instance to release the
  single-instance name before launching the measured one.
• User-facing checksum instructions point at the published SHA256SUMS
  file used since 0.0.6.