feat(audio-cpp): add ROCm backend image

The pinned audio.cpp revision supports HIP, but LocalAI neither builds a ROCm image nor accepts its backend option. AMD hosts therefore fall back to the CPU image.

Build and publish the HIP variant, connect it to AMD capability selection, and accept both upstream HIP names.

Assisted-by: Codex:gpt-5
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

backend/cpp/audio-cpp/model_options_test.cpp

@@ -75,6 +75,11 @@ static void test_scalar_options() {
     check(parse_model_options({"live_idle_timeout_ms:0"}).options.live_idle_timeout_ms == 0,
           "an explicit 0 turns the live idle limit off rather than reverting to "
           "the default");
+
+    check(parse_model_options({"backend:hip"}).error.empty(),
+          "HIP backend option is accepted");
+    check(parse_model_options({"backend:rocm"}).error.empty(),
+          "ROCm backend alias is accepted");
 }
 
 // Values containing colons must survive: split on the FIRST colon only.
@@ -124,6 +129,8 @@ static void test_errors() {
           "negative device is rejected");
     check(!parse_model_options({"threads:x"}).error.empty(),
           "non-numeric threads is rejected");
+    check(!parse_model_options({"backend:unknown"}).error.empty(),
+          "unknown compute backend is rejected before model loading");
 
     // Values too large for int must be rejected, not silently wrapped into a
     // negative device index that then reaches the ggml backend selector.