Add external configuration file system

Breaking Changes:
- Configuration now via config.json instead of editing Python code
- Remove all hardcoded paths (no more /home/berwn)
- Separate system config (config.json) from runtime config (user_config.json)

Features:
- config.example.json with all configurable options
- GPIO pin and state configuration
- Audio device index configuration
- Customizable paths (relative or absolute)
- Web port and upload size settings
- No code editing required for deployment

Configuration Structure:
- gpio: hook_pin, hook_pressed_state
- audio: device_index, chunk_size, channels, sample_rate, max_record_seconds
- paths: base_dir, recordings_dir, sounds_dir
- web: port, max_upload_size_mb
- system: active_greeting, default_volume

Script automatically:
- Checks for config.json on startup
- Provides helpful error if missing
- Uses relative paths by default
- Loads test_complete.py config from same file

Updated Documentation:
- Complete configuration guide in README
- Setup instructions without hardcoded paths
- Troubleshooting for config errors
- Device index discovery command

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

test_complete.py

@@ -8,10 +8,28 @@ import wave
 import numpy as np
 import time
 import os
+import json
+import sys
 
-# HiFiBerry device index (from your system)
-HIFIBERRY_INDEX = 1
-SAMPLE_RATE = 44100
+# Load configuration
+def load_config():
+    """Load audio device configuration"""
+    config_path = os.path.join(os.path.dirname(os.path.abspath(__file__)), 'config.json')
+
+    if not os.path.exists(config_path):
+        print("Config file not found. Using default device index 1")
+        return {"audio": {"device_index": 1, "sample_rate": 44100}}
+
+    try:
+        with open(config_path, 'r') as f:
+            return json.load(f)
+    except:
+        print("Error reading config. Using defaults.")
+        return {"audio": {"device_index": 1, "sample_rate": 44100}}
+
+CONFIG = load_config()
+HIFIBERRY_INDEX = CONFIG['audio']['device_index']
+SAMPLE_RATE = CONFIG['audio']['sample_rate']
 
 def test_playback():
     """Test speaker output"""