[fix](trx-rs): install binaries under user home

Default installation and removal to /home/sjg/.local/bin while preserving explicit prefix and binary-directory overrides. Update the service examples and README to match.

Assisted-By: OpenAI Codex (GPT-5)
Signed-off-by: Stan Grams <sjg@haxx.space>

script/install.sh

@@ -15,7 +15,7 @@ PROJECT_ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"
 BINARIES=(trx-server trx-client trx-configurator)
 
 # --- Defaults (override via flags or environment) ---------------------------
-PREFIX="${PREFIX:-/usr/local}"
+PREFIX="${PREFIX:-$HOME/.local}"
 BINDIR="${BINDIR:-}"          # derived from PREFIX unless set explicitly
 NO_SDR=0
 DO_BUILD=1
@@ -33,7 +33,7 @@ Usage: script/install.sh [options]
 Build trx-rs (release) and install it.
 
 Options:
-  --prefix DIR     Install prefix; binaries go to DIR/bin (default: /usr/local)
+  --prefix DIR     Install prefix; binaries go to DIR/bin (default: \$HOME/.local)
   --bindir DIR     Install binaries directly to DIR (overrides --prefix)
   --no-sdr         Build without SoapySDR support (--no-default-features)
   --no-build       Skip cargo build; install existing target/release binaries