v0.3.8

fix(bridge): tolerate slow server pongs + paint status dots green/red

Two user-visible fixes:

1. WS stability: ping_timeout increased 20s → 60s and app-level
   heartbeat tightened 30s → 15s. The earlier 20/30 combo was dropping
   the connection after ~90s whenever the server's event loop stalled
   briefly on a DB commit — taking any in-flight print job down with
   it, which is why "Plătește" at the POS was returning "bridge
   disconnected". The server fix (backend commit 6af6064) already
   reduced the stalls; this client-side slack closes the remaining gap.

2. GUI: the Stare indicators ("Proces", "Conexiune 360booking", "Casa
   de marcat") showed a gray dot in every state because ttk.Label
   ignores foreground configure() on Windows themes. Switched to
   tk.Label with an explicit fg, kept a reference to each dot, and
   _set_dot now paints them green (#1f883d) / red (#cf222e) / gray so
   the user can tell at a glance whether the bridge is healthy.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>