refactor: split into independent trx-server and trx-client binaries

Delete trx-bin (all-in-one) and trx-bin-common (shared lib). Each binary
now has its own config, plugins, and helper modules inlined.

- trx-server: backend-only daemon with ServerConfig (general, rig, behavior)
  no frontend dependencies
- trx-client: remote client with ClientConfig (general, remote, frontends)
  includes all frontend support (http, rigctl, http-json, qt)
- Dedicated config files: trx-server.toml / trx-client.toml

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/trx-server/Cargo.toml

@@ -0,0 +1,21 @@
+# SPDX-FileCopyrightText: 2025 Stanislaw Grams <stanislawgrams@gmail.com>
+#
+# SPDX-License-Identifier: BSD-2-Clause
+
+[package]
+name = "trx-server"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+tokio = { workspace = true, features = ["full"] }
+tokio-serial = { workspace = true }
+serde = { workspace = true, features = ["derive"] }
+toml = { workspace = true }
+tracing = { workspace = true }
+tracing-subscriber = { workspace = true }
+clap = { workspace = true, features = ["derive"] }
+dirs = "6"
+libloading = "0.8"
+trx-backend = { path = "../trx-backend" }
+trx-core = { path = "../trx-core" }