Add auto-update for missing configuration settings

Implemented automatic config file updates to add missing settings
with default values on startup. This eliminates manual config
editing when upgrading to newer versions.

Features:
- Auto-updates config.json with missing settings
- Auto-updates user_config.json with missing user preferences
- Console logging shows which settings were added
- Preserves existing values - only adds missing keys
- Writes updated config back to file automatically
- Graceful error handling if write fails

System config (config.json):
- Comprehensive defaults for all sections
- GPIO, audio, paths, backup, web, system settings
- New settings like volume_greeting, volume_button, volume_beep

User config (user_config.json):
- Loop-based checking against default_config
- Automatic save when updates are detected
- Error logging for troubleshooting

Benefits:
- Seamless upgrades without manual config edits
- No breaking changes when new features are added
- Users see exactly what was added in console
- Backward compatible with old config files

Example console output:
  [CONFIG] Added missing setting: system.volume_beep = 70
  [CONFIG] Updated config.json with missing defaults
  [USER_CONFIG] Added missing setting: volume_button = 70
  [USER_CONFIG] Updated user_config.json with missing defaults

Updated README.md to document auto-update feature.

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

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

README.md

@@ -491,6 +491,18 @@ rotary_phone_data/            # Default location (configurable)
 
 All configuration is done via the `config.json` file. **No need to edit Python code!**
 
+### Auto-Update Feature
+
+The system automatically adds missing configuration settings with default values when it starts:
+
+- **config.json** - System configuration is auto-updated with any missing settings
+- **user_config.json** - User settings are auto-updated with new defaults
+- Console shows which settings were added: `[CONFIG] Added missing setting: system.volume_beep = 70`
+- Original config is preserved - only missing keys are added
+- No manual editing required when upgrading to newer versions
+
+This means you can upgrade the code and your old config files will work automatically!
+
 ### Configuration File Structure
 
 The `config.json` file contains all system settings:

rotary_phone_web.py

@@ -24,7 +24,7 @@ import io
 
 # Load configuration
 def load_system_config():
-    """Load system configuration from config.json"""
+    """Load system configuration from config.json and auto-update with missing defaults"""
     config_path = os.path.join(os.path.dirname(os.path.abspath(__file__)), 'config.json')
 
     # Check if config exists, otherwise use example
@@ -39,7 +39,77 @@ def load_system_config():
             sys.exit(1)
 
     with open(config_path, 'r') as f:
-        return json.load(f)
+        config = json.load(f)
+
+    # Default values for all settings
+    defaults = {
+        'gpio': {
+            'hook_pin': 17,
+            'hook_pressed_state': 'LOW',
+            'extra_button_enabled': False,
+            'extra_button_pin': 27,
+            'extra_button_pressed_state': 'LOW'
+        },
+        'audio': {
+            'device_index': 1,
+            'chunk_size': 1024,
+            'format': 'paInt16',
+            'channels': 1,
+            'sample_rate': 48000,
+            'max_record_seconds': 300
+        },
+        'paths': {
+            'base_dir': './rotary_phone_data',
+            'recordings_dir': 'recordings',
+            'sounds_dir': 'sounds'
+        },
+        'backup': {
+            'enabled': True,
+            'usb_paths': ['/media/usb0', '/media/usb1'],
+            'verify_crc': True,
+            'backup_on_write': True
+        },
+        'web': {
+            'port': 8080,
+            'max_upload_size_mb': 50
+        },
+        'system': {
+            'active_greeting': 'dialtone.wav',
+            'extra_button_sound': 'button_sound.wav',
+            'beep_sound': 'beep.wav',
+            'beep_enabled': True,
+            'greeting_delay_seconds': 0,
+            'volume': 70,
+            'volume_greeting': 70,
+            'volume_button': 70,
+            'volume_beep': 70
+        }
+    }
+
+    # Check if any defaults are missing and add them
+    updated = False
+    for section, section_defaults in defaults.items():
+        if section not in config:
+            config[section] = section_defaults
+            updated = True
+            print(f"[CONFIG] Added missing section: {section}")
+        else:
+            for key, default_value in section_defaults.items():
+                if key not in config[section]:
+                    config[section][key] = default_value
+                    updated = True
+                    print(f"[CONFIG] Added missing setting: {section}.{key} = {default_value}")
+
+    # Save updated config if changes were made
+    if updated:
+        try:
+            with open(config_path, 'w') as f:
+                json.dump(config, f, indent=2)
+            print(f"[CONFIG] Updated config.json with missing defaults")
+        except Exception as e:
+            print(f"[CONFIG] Warning: Could not save updated config: {e}")
+
+    return config
 
 # Load system configuration
 SYS_CONFIG = load_system_config()
@@ -274,23 +344,27 @@ class RotaryPhone:
             try:
                 with open(USER_CONFIG_FILE, 'r') as f:
                     config = json.load(f)
-                    # Ensure required keys exist
-                    if "volume" not in config:
-                        config["volume"] = SYS_CONFIG['system']['volume']
-                    if "volume_greeting" not in config:
-                        config["volume_greeting"] = SYS_CONFIG['system'].get('volume_greeting', 70)
-                    if "volume_button" not in config:
-                        config["volume_button"] = SYS_CONFIG['system'].get('volume_button', 70)
-                    if "volume_beep" not in config:
-                        config["volume_beep"] = SYS_CONFIG['system'].get('volume_beep', 70)
-                    if "greeting_delay" not in config:
-                        config["greeting_delay"] = SYS_CONFIG['system'].get('greeting_delay_seconds', 0)
-                    if "beep_enabled" not in config:
-                        config["beep_enabled"] = SYS_CONFIG['system'].get('beep_enabled', True)
-                    if "beep_sound" not in config:
-                        config["beep_sound"] = SYS_CONFIG['system'].get('beep_sound', 'beep.wav')
+
+                    # Check for missing keys and add defaults
+                    updated = False
+                    for key, default_value in default_config.items():
+                        if key not in config:
+                            config[key] = default_value
+                            updated = True
+                            print(f"[USER_CONFIG] Added missing setting: {key} = {default_value}")
+
+                    # Save updated config if changes were made
+                    if updated:
+                        try:
+                            with open(USER_CONFIG_FILE, 'w') as fw:
+                                json.dump(config, fw, indent=2)
+                            print(f"[USER_CONFIG] Updated user_config.json with missing defaults")
+                        except Exception as e:
+                            print(f"[USER_CONFIG] Warning: Could not save updated config: {e}")
+
                     return config
-            except:
+            except Exception as e:
+                print(f"[USER_CONFIG] Error loading user config: {e}, using defaults")
                 pass
 
         return default_config