Critical fix
- Auto-updater broken since v2.5.0 — the "Check for updates" button and silent startup check were both failing silently due to accumulated signal connections. Fixed by disconnecting stale handlers before each check.
- Added redirect policy and 15-second timeout to update API requests
- Users on v2.5.0 through v2.6.0 must update manually this one time — the updater will work correctly from v2.6.1 onward