Remove unused MCP resources and update documentation

- Remove array_status, system_info, notifications_overview, and parity_status resources
- Keep only logs_stream resource (unraid://logs/stream) which is working properly
- Update README.md with current resource documentation and modern docker compose syntax
- Fix import path issues that were causing subscription errors
- Update environment configuration examples
- Clean up subscription manager to only include working log streaming

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

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

unraid_mcp/core/exceptions.py

@@ -0,0 +1,48 @@
+"""Custom exceptions for Unraid MCP Server.
+
+This module defines custom exception classes for consistent error handling
+throughout the application, with proper integration to FastMCP's error system.
+"""
+
+from fastmcp.exceptions import ToolError as FastMCPToolError
+
+
+class ToolError(FastMCPToolError):
+    """User-facing error that MCP clients can handle.
+
+    This is the main exception type used throughout the application for
+    errors that should be presented to the user/LLM in a friendly way.
+
+    Inherits from FastMCP's ToolError to ensure proper MCP protocol handling.
+    """
+    pass
+
+
+class ConfigurationError(ToolError):
+    """Raised when there are configuration-related errors."""
+    pass
+
+
+class UnraidAPIError(ToolError):
+    """Raised when the Unraid API returns an error or is unreachable."""
+    pass
+
+
+class SubscriptionError(ToolError):
+    """Raised when there are WebSocket subscription-related errors."""
+    pass
+
+
+class ValidationError(ToolError):
+    """Raised when input validation fails."""
+    pass
+
+
+class IdempotentOperationError(ToolError):
+    """Raised when an operation is idempotent (already in desired state).
+
+    This is used internally to signal that an operation was already complete,
+    which should typically be converted to a success response rather than
+    propagated as an error to the user.
+    """
+    pass