feat: Add SCIM 2.0 support for enterprise user provisioning

Implements SCIM 2.0 protocol for automated user and group provisioning from identity providers like Okta, Azure AD, and Google Workspace.

Backend changes:
- Add SCIM configuration with PersistentConfig for database persistence
- Implement SCIM 2.0 endpoints (Users, Groups, ServiceProviderConfig)
- Add bearer token authentication for SCIM requests
- Include comprehensive test coverage for SCIM functionality

Frontend changes:
- Add SCIM admin settings page with token generation
- Implement SCIM configuration management UI
- Add save functionality and proper error handling
- Include SCIM statistics display

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

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

backend/open_webui/config.py

@@ -778,6 +778,22 @@ ENABLE_DIRECT_CONNECTIONS = PersistentConfig(
     os.environ.get("ENABLE_DIRECT_CONNECTIONS", "True").lower() == "true",
 )
 
+####################################
+# SCIM Configuration
+####################################
+
+SCIM_ENABLED = PersistentConfig(
+    "SCIM_ENABLED",
+    "scim.enabled",
+    os.environ.get("SCIM_ENABLED", "False").lower() == "true",
+)
+
+SCIM_TOKEN = PersistentConfig(
+    "SCIM_TOKEN",
+    "scim.token",
+    os.environ.get("SCIM_TOKEN", ""),
+)
+
 ####################################
 # OLLAMA_BASE_URL
 ####################################