feat: in-place torch upgrade with rollback (detection + pill + backgr…

[cryptopoly]

…ound job)

Adds a self-contained path for users with a working CUDA torch install to upgrade to a newer wheel without re-running the full 2.5 GB GPU bundle. Surfaces as a compact pill in the Image / Video Studio runtime banners when realGenerationAvailable AND the matching cu{N} pip index serves a newer wheel than the one on disk; silent otherwise.

Backend

• _install_helpers.py: _extract_cuda_tag, _index_url_for_cuda_tag, _parse_version_triple, _classify_torch_upgrade, _query_latest_torch_version (pip index versions parser, both output shapes), _abi_dependents_present, _move_torch_to_rollback + _restore_torch_from_rollback + _cleanup_old_torch_rollbacks, _TORCH_ABI_DEPENDENT_PACKAGES constant.
• routes/setup/torch_upgrade.py: GET /api/setup/torch-upgrade-available (synchronous detection, returns {available, current, latest, upgradeType, rebuildPackages, indexUrl} or {available: false, reason}) and POST /api/setup/upgrade-torch (background job mirroring install-gpu-bundle pattern). Worker moves existing torch to .torch-rollback-<version>/ instead of purging, installs target from the same cu{N} index, re-pins constraint, force-reinstalls ABI deps on minor/major bumps (bitsandbytes/torchao/nunchaku/sageattention), verifies CUDA in a subprocess, restores rollback on verify failure, keeps the most recent rollback as a safety net.

Frontend

• src/api/setup.ts: checkTorchUpgradeAvailable, startTorchUpgrade, getTorchUpgradeStatus + 4 exported types. Re-exported via src/api/index.ts.
• src/components/TorchUpgradePill.tsx: one-shot probe on mount, hides when available: false, three display states (available / in-progress / done-or-error), polls status at 1.5 Hz with cleanup keyed by job.done, inline collapsible install log with phase-named markers. Restart Backend hook plumbed through.
• src/styles.css: color-coded badges per upgrade type (patch=green / minor=amber / major=red).
• Wired into ImageStudioRuntimeBanner + VideoStudioRuntimeBanner; renders only when realGenerationAvailable so users with broken torch are not second-guessed.

Tests

• 24 new tests in tests/test_setup_routes.py covering every helper (version parsing edge cases including 2.6.0rc1 that caught a real bug in the first cut where digits across non-digit boundaries leaked into the parsed triple), both pip output shapes, rollback move/restore round-trip with simulated half-install in extras, cleanup mtime ordering, and all 8 detection-response shapes plus the apple-silicon rejection and running-job POST cases.

Drive-by: package-lock.json version field was lagging at 0.8.0 after the 0.9.0 bump; synced.

Verified: 24/24 new tests pass, 80/80 test_setup_routes.py pass, 217/217 setup + backend + services + inference pass, 371/371 vitest pass, tsc --noEmit clean. Pre-existing test_cache_strategies / test_sdcpp_* / test_preview_thumbnails failures verified to exist on baseline (Windows env + optional diffusers deps), unrelated.