Bump to 1.7.0-beta.2

[Pixnop]

One line: the version becomes 1.7.0-beta.2. Everything else for the release is already on dev.

What ships in this beta, for whoever writes or reviews the release notes: the Windows install fix for the false hard-link refusals (#168, the #119 field report), registering already-installed versions from a folder with the linked flag protecting user folders on uninstall (#138, #164, closing #120), the user-data migration to the RiftLauncher folder with its one-time copy (#114, #160; every migrating player signs in again once, worth a bold line in the notes), auto-update coverage for deb, rpm and pacman with the system password prompt on those formats (#124, #167), the full rebrand down to the freedesktop icons and the wiki (#156, #162, #163), the task-status and backups fixes, and the perf pass (#169).

After this merges, the plan is: tag v1.7.0-beta.2 on main after promotion, let the release workflow build the six-plus artifacts (now including rpm and pacman for the first time), verify the draft, publish as a prerelease, and then run the real proof: an installed beta.1 discovering and applying the update to beta.2 on its own, which is the one link of the chain that has never been exercised end to end.

[Zaldaryon]

Reviewed the version bump and its lockfile. package.json and package-lock.json are synchronized at 1.7.0-beta.2, the version is semver-valid, and the diff is limited to those two files. The required typecheck, lint, test, and Ubuntu and Windows build checks pass. Approving this change for merge into dev. Before promoting beta.2, decide whether PRs #176 and #177 belong in this release, run the non-publishing installer smoke tests for AppImage, deb, rpm, pacman, and Windows, and verify the generated release metadata.