v0.51.10 — 2-PR batch (cron profile isolation + profile switch during streams)

🐛 Fixed

#1741 by @Michaelyklam — Isolate in-process cron scheduler profiles. Closes #1575. Defensive future-architectural fix: a future in-process scheduler tick path would otherwise run jobs with whatever process-global profile happened to be active. New install_cron_scheduler_profile_isolation() wraps cron.scheduler.run_job() to enter the job's persisted profile context. Manual /api/crons/run flow is unchanged.
#1742 by @Michaelyklam — Allow profile switching during active streams. Closes #1700. Per-client cookie/thread-local profile switches (process_wide=False) are no longer blocked by an active stream — only true process-global mutations remain blocked. Frontend creates a fresh session for the target profile rather than retagging the running one.

i18n cleanup: removed 9 orphaned profiles_busy_switch keys (the toast was deleted by #1742; entries had no remaining consumer).

4590 → 4596 passing (+6 regression tests). 0 regressions.

Both PRs CI-green + rebased onto current origin/master with sibling-rebase on api/profiles.py (different regions).
All JS files syntax-clean (node -c).
Browser API sanity (11/11 endpoints) — all pass.
Startup-hook verification: install_cron_scheduler_profile_isolation() is idempotent and crash-free.
Opus advisor: SHIP both, 5/5 verification clean, 0 MUST-FIX, 1 SHOULD-FIX absorbed (orphaned i18n keys).

Full Changelog: v0.51.9...v0.51.10