feat: Add XTTS v2 support, refactor Docker/GPU infra, and improve Piper engine

- Add XTTS v2 configuration to .env.example
- Refactor Dockerfile to multi-stage build with CUDA 12.1 support
- Update Makefile with Kokoro and XTTS test environment targets
- Refactor Piper engine (app/engines/piper.py) to use python module execution
- Add comprehensive documentation for Kokoro and XTTS plans
- Add helper scripts and patches for build process

scripts/tts_client.py

@@ -0,0 +1,79 @@
+#!/usr/bin/env python3
+"""
+A simple CLI client to test the AudioEngineHub TTS server.
+
+This script requires the 'requests' library.
+Install it with: pip install requests
+"""
+
+import argparse
+import requests
+import os
+from urllib.parse import urljoin
+
+def main():
+    parser = argparse.ArgumentParser(description="CLI client for AudioEngineHub TTS server.")
+    parser.add_argument("--server-url", required=True, help="Base URL of the TTS server (e.g., http://localhost:8000).")
+    parser.add_argument("--text", required=True, help="Text to synthesize.")
+    parser.add_argument("--engine", required=True, help="TTS engine to use (e.g., piper).")
+    parser.add_argument("--model", help="Model to use (optional).")
+    parser.add_argument("--speaker", help="Speaker to use (optional).")
+    parser.add_argument("--output", required=True, help="Path to save the output audio file (e.g., output.ogg).")
+    
+    args = parser.parse_args()
+
+    # --- 1. Make the TTS request ---
+    tts_url = urljoin(args.server_url, "/tts")
+    payload = {
+        "text": args.text,
+        "engine": args.engine,
+        "format": "ogg" # Or determine from output file extension
+    }
+    if args.model:
+        payload["model"] = args.model
+    if args.speaker:
+        payload["speaker"] = args.speaker
+
+    print(f"Requesting synthesis from {tts_url} with payload: {payload}")
+    # Add a short delay to mitigate potential connection race conditions
+    import time
+    time.sleep(1)
+    try:
+        response = requests.post(tts_url, json=payload)
+        response.raise_for_status() # Raise an exception for bad status codes (4xx or 5xx)
+    except requests.exceptions.RequestException as e:
+        print(f"ERROR: Could not connect to the server: {e}")
+        return
+
+    try:
+        data = response.json()
+    except requests.exceptions.JSONDecodeError:
+        print(f"ERROR: Failed to decode JSON response from server. Response text: {response.text}")
+        return
+
+    if "audio_url" not in data:
+        print(f"ERROR: Server response did not contain 'audio_url'. Response: {data}")
+        return
+
+    # --- 2. Download the audio file ---
+    audio_url = urljoin(args.server_url, data["audio_url"])
+    print(f"Downloading audio from {audio_url}...")
+    
+    try:
+        audio_response = requests.get(audio_url, stream=True)
+        audio_response.raise_for_status()
+    except requests.exceptions.RequestException as e:
+        print(f"ERROR: Could not download the audio file: {e}")
+        return
+
+    # --- 3. Save the audio file ---
+    try:
+        with open(args.output, "wb") as f:
+            for chunk in audio_response.iter_content(chunk_size=8192):
+                f.write(chunk)
+        print(f"Successfully saved audio to '{args.output}'")
+    except IOError as e:
+        print(f"ERROR: Could not write to output file '{args.output}': {e}")
+
+if __name__ == "__main__":
+    main()