fix(nightly-v2): unblock releases and defer optional features

[saphid]

What changed

Restore the Fork V2 release pipeline with the updater and bug fixes retained. Defer the optional voice, deep-link, external-file-link, and build-metadata features to separate follow-up work. Their immutable pins and recovery branch are recorded in docs/operations/ov2-deferred-features.md.

Why

Scheduled V2 releases stopped at the custom updater patch after upstream changed desktop profile isolation. Refresh that patch for the new profile and APIs, retire the replay-gate test patch now supplied upstream, and adapt the retained provider-recovery test fixture to the new projection queries. Optional features must not delay a working V2 release.

Verification

• Reproduced the scheduled release conflict, then replayed all 14 selected patches cleanly on upstream 32490b9fcbb1e3b5f19f5c687c343295cf1a1751 using the production assembler.
• Assembler tests: 22 passed.
• Focused desktop updater, identity, connection catalog, provider recovery, and packaging tests: 201 passed.
• Desktop, web, server, and contracts typechecks passed.
• Formatter checks on manually resolved files and git diff --check passed.
• Hosted full checks and packaging run after activation. No new release is claimed yet.