ac0c16c97b
Flask's default cookie name ('session') is shared across all ports on the same
hostname. When two PIC instances are accessed via localhost:portA and localhost:portB,
logging into one overwrites the other's session cookie, causing repeated logouts.
Derive a unique 8-hex suffix from each instance's persistent SECRET_KEY and set
SESSION_COOKIE_NAME = 'pic_sess_<suffix>'. This ensures each cell uses a distinct
cookie name, so sessions are fully isolated regardless of hostname.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>