Refactor golden image handling in backup upload process</message>

<message>Update the _set_golden_from_path function to improve the handling of existing golden image files. Replace the existing unlink logic with a more robust method that safely removes files or broken symlinks using the missing_ok parameter. This change enhances the reliability of the backup upload process by ensuring that stale references are properly cleared before setting a new golden image path.

backup-from-device/gnss-guard/tm-gnss-guard/server/config.py

@@ -0,0 +1,75 @@
+#!/usr/bin/env python3
+"""
+Server configuration management for GNSS Guard Server
+Loads configuration from environment variables
+"""
+
+import os
+import sys
+from pathlib import Path
+from typing import Optional
+from pydantic_settings import BaseSettings
+from pydantic import field_validator
+
+
+class ServerConfig(BaseSettings):
+    """Server configuration loaded from environment variables"""
+    
+    # Server settings
+    server_host: str = "0.0.0.0"
+    server_port: int = 8000
+    debug: bool = False
+    
+    # Database settings (PostgreSQL) - REQUIRED, no insecure default
+    database_url: str
+    
+    # Security settings
+    secret_key: str = "change-this-in-production-to-a-random-secret-key"
+    session_expire_minutes: int = 1440  # 24 hours
+    
+    # Web UI authentication - REQUIRED, no insecure defaults
+    # Must be set via environment variables GNSS_SERVER_WEB_USERNAME and GNSS_SERVER_WEB_PASSWORD
+    web_username: str
+    web_password: str
+    
+    @field_validator('web_password')
+    @classmethod
+    def password_strength(cls, v: str) -> str:
+        """Ensure password meets minimum security requirements"""
+        if len(v) < 10:
+            raise ValueError('Password must be at least 10 characters long')
+        if v.lower() in ['password', 'admin', 'test', '123456', 'tototheo']:
+            raise ValueError('Password is too common/weak')
+        return v
+    
+    # Validation settings
+    stale_threshold_seconds: int = 60  # Data older than this is considered stale
+    
+    # Asset offline detection
+    asset_offline_seconds: int = 120  # Consider asset offline after this many seconds without updates
+    
+    # Data retention
+    validation_history_days: int = 90  # Keep 90 days of validation history
+    
+    # Domain for SSL (optional)
+    server_domain: Optional[str] = None
+    
+    # Telegram notification settings (optional)
+    telegram_bot_token: Optional[str] = None
+    telegram_chat_id: Optional[str] = None  # Default chat ID for all assets
+    
+    @property
+    def telegram_enabled(self) -> bool:
+        """Check if Telegram notifications are configured"""
+        return bool(self.telegram_bot_token and self.telegram_chat_id)
+    
+    class Config:
+        env_file = ".env"
+        env_prefix = "GNSS_SERVER_"
+        case_sensitive = False
+
+
+def get_config() -> ServerConfig:
+    """Get server configuration instance"""
+    return ServerConfig()
+