Add configurable admin password via environment variable

backend/app/config.py

@@ -53,6 +53,9 @@ class Settings(BaseSettings):
     log_level: str = "INFO"  # DEBUG, INFO, WARNING, ERROR, CRITICAL
     log_format: str = "auto"  # "json", "standard", or "auto" (json in production)
 
+    # Initial admin user settings
+    admin_password: str = ""  # Initial admin password (if empty, uses 'changeme123')
+
     # JWT Authentication settings (optional, for external identity providers)
     jwt_enabled: bool = False  # Enable JWT token validation
     jwt_secret: str = ""  # Secret key for HS256, or leave empty for RS256 with JWKS