Proofing Gallery 0.6.2

• repair legacy gallery share tokens with a new idempotent upgrade migration
  while preserving existing primary public links and archived-gallery safety
• update the transitive build-time fast-uri dependency to 3.1.5 to resolve
  GHSA-7p8r-x3mc-p8w7 without unrelated lockfile churn
• stabilize owner-dashboard visual verification and retain Playwright reports,
  traces, screenshots, and videos when browser CI fails
• add reproducible signed packages and protected publication to the Nextcloud
  App Store alongside checksums, an SPDX SBOM, and artifact attestations