Rigflow 1.1.1 — Hermes Lite 2 discovery on wide subnets

A small fix release. The headline is a discovery bug that made a Hermes Lite 2 invisible
on some home networks — reported, with a decisive packet capture, by @cdstg.

✅ Client and server can be upgraded independently this time. Unlike 1.1.0, this
release changes nothing in the client↔server protocol. The fix is server-side, so an
existing 1.1.0 client works against a 1.1.1 server and vice-versa.

Fixed

• A Hermes Lite 2 could go undiscovered on subnets wider than /24. If your router hands
  out a /22 or /16 — some mesh systems do by default — the server found no radio at all,
  silently, and Rescan didn't help, while other SDR software found the same rig
  normally. Discovery now probes the broadcast address the radio actually accepts, in
  addition to the subnet broadcast. (#43)
• New --hl2-ip ADDR[,ADDR] server option probes a Hermes Lite 2 directly by address,
  in addition to the normal broadcast. For networks where broadcast can't reach the radio
  at all — a routed segment, a VLAN, or an access point that filters broadcast traffic.

Documentation

• The client's media port is now documented. The server streams audio and waterfall to
  the client on UDP 50000. A firewall on the client machine lets you connect and
  control the radio while leaving the spectrum flat and silent — everything looks connected
  but no media arrives. The installation guide's port list now covers both directions, and
  troubleshooting has an entry for that exact symptom.
• Troubleshooting gained an entry for "other software finds my HL2 but Rigflow doesn't",
  and a note that the server's log level comes from RUST_LOG, not a command-line flag.

Compatibility

Mix and match with 1.1.0 as needed — no protocol change. See the
Installation guide
for runtime libraries.

Known issues

• FT8 on Linux (PipeWire): a short beep at the end of each over — cosmetic; the TCI
  transport is clean if it bothers you.
• Receive CW decodes both sidebands (symmetric); AGC is single-rate.

Disclaimer

Rigflow controls transmitters and amplifiers — operate within your license and verify your
signal. See the
Disclaimer.

Thanks to @cdstg for the report and the tcpdump that pinned it down, and to
@chrisdebian for unit-test coverage across the shared DSP and VFO types.

Full changelog: v1.1.0...v1.1.1