Refactor workflow state extraction to use generic helper

[Copilot]

Backend workflow activities contained repetitive state extraction boilerplate—each value required 6-8 lines of manual type assertions and error handling.

Changes

• Centralized state helper: Extracted existing getFromState[T] generic from deployer_activities.go into shared state_helpers.go
• Refactored activities: Applied helper to 15 step functions across user_activities.go (11 functions) and node_activities.go (4 functions)
• Net impact: -96 lines of repetitive code

Example

Before:

emailVal, ok := state["email"]
if !ok {
    return fmt.Errorf("missing 'email' in state")
}
email, ok := emailVal.(string)
if !ok {
    return fmt.Errorf("'email' in state is not a string")
}

After:

email, err := getFromState[string](state, "email")
if err != nil {
    return err
}

The helper handles both direct type assertions and JSON marshaling/unmarshaling for persisted workflow state.

Original prompt

revise the dataflow in the backend

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