feat(08): implement SSOT architecture for network configuration

config/backend.yaml.example

@@ -35,21 +35,8 @@ ai:
   # Environment: BACKEND_AI_FALLBACK_PROVIDER
   fallback_provider: "claude"
 
-  # Gemini API Key (obtain from https://aistudio.google.com/)
-  # Environment: BACKEND_AI_GEMINI_API_KEY or GEMINI_API_KEY
-  gemini_api_key: "your-gemini-api-key"
-
-  # Claude API Key (obtain from Anthropic Console)
-  # Environment: BACKEND_AI_CLAUDE_API_KEY or CLAUDE_API_KEY
-  claude_api_key: "your-claude-api-key"
-
 # --- Authentication & LDAP ---
 auth:
-  # JWT Secret Key (min 32 chars)
-  # Generate with: openssl rand -hex 32
-  # Environment: BACKEND_AUTH_JWT_SECRET_KEY or JWT_SECRET_KEY
-  jwt_secret_key: "change_me_in_production"
-
   # Enable LDAP Authentication?
   # Default: false
   # Environment: BACKEND_AUTH_LDAP_ENABLED or LDAP_ENABLED