PacketQueue::countBefore() and PacketQueue::get() use unsigned
comparison (_schedule_table[j] > now) to check if a packet is
scheduled for the future. This breaks when millis() wraps around
after ~49.7 days: packets scheduled just before the wrap appear
to be in the far future and get stuck in the queue.
Use signed subtraction instead, matching the approach already used
by Dispatcher::millisHasNowPassed(). This correctly handles the
wraparound for time differences up to ~24.8 days in either
direction, well beyond the maximum queue delay of 32 seconds.
PacketQueue::add() silently dropped packets when the queue was at
capacity. The packet pointer was lost — never enqueued, never returned
to the unused pool. Each occurrence permanently shrank the 32-packet
pool until allocNew() returned NULL and the node went deaf. Return bool
from add() and free the packet back to the pool on failure.
