feat(diffusers): add AudioLDM2 generation

Expose diffusers audio pipelines through the existing sound-generation RPC. AudioLDM2 can now return PCM WAV output from the model gallery without a separate backend.

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

backend/python/diffusers/audio_utils.py

@@ -0,0 +1,24 @@
+import array
+import sys
+import wave
+
+
+def write_pcm_wav(destination, samples, sampling_rate):
+    """Write normalized floating-point audio samples as mono 16-bit PCM."""
+    pcm = array.array(
+        "h",
+        (
+            max(-32768, min(32767, round(float(sample) * 32768)))
+            for sample in samples
+        ),
+    )
+    if pcm.itemsize != 2:
+        raise RuntimeError("16-bit PCM requires two-byte signed integers")
+    if sys.byteorder != "little":
+        pcm.byteswap()
+
+    with wave.open(destination, "wb") as output:
+        output.setnchannels(1)
+        output.setsampwidth(2)
+        output.setframerate(sampling_rate)
+        output.writeframes(pcm.tobytes())