fix:Fixes to UI and Flux Alpha Scaling

[hipsterusername]

Training UI Controls & Process Management

• Added "Start Training", "Stop Training", and "Training Status" controls to the Gradio UI, allowing users to start, stop, and monitor training directly from the interface. The UI now disables/enables buttons appropriately based on training activity, and provides real-time status updates. [1] [2] [3]
• Implemented backend support for stopping training processes and checking if training is active, including graceful termination and status reporting. [1] [2]
• Integrated the new training control callbacks into all pipeline tabs, ensuring consistent behavior across different training types. [1] [2] [3] [4] [5] [6] [7]

Flux LoRA Configuration Enhancements

• Added UI options for training the text encoder (train_text_encoder) and specifying its learning rate (text_encoder_learning_rate), alongside existing transformer options. These are now reflected throughout the config group logic and UI output components. [1] [2] [3]
• Updated the LoRA layer injection logic to set lora_alpha based on the configured rank dimension, aligning with Diffusers' conventions for improved training behavior.

Validation Prompts Handling

• Improved conversion between UI and internal representations of validation prompts, ensuring correct processing of positive/negative prompts and robust error handling. [1] [2] [3]

These changes collectively enhance the usability, configurability, and reliability of the training pipelines and their user interfaces.