Unstable inputs fix

• Unstable inputs: clicks were lost intermittently (issue #2). The UDP listener
  socket (port 4646) was opened with SO_REUSEPORT; on Linux the kernel then
  spreads incoming datagrams across every socket bound to that port. After a reload,
  an update or a restart, an old socket sometimes stayed bound and "stole" a share
  of the WAGO INT packets, which were silently lost. The socket is now
  exclusive: every input packet reaches the single listening instance.
• Clean close of the UDP socket on unload (waiting for its actual release) and a
  bind retry at startup, so a reload never leaves two sockets competing for the port.

Added

• A bus event wago2haddon_event is fired on every decoded action (single /
  double / triple click, long press), in addition to the event entity. An event
  trigger on this event is fully reliable (never de-duplicated) and is a robust
  alternative for automations.
• Defensive handling of multiple messages per datagram (no message dropped if the
  PLC were to batch them).
• Clean cancellation of the input decoder timers when an entity is removed (avoids
  an event firing after a reload).