Implement status bar updates during fitting

[rozyczko]

This pull request introduces improvements to the fitting progress reporting and user interface feedback in ERA. The changes add new properties and signals to track and display in-flight fitting progress, such as current iteration, interim chi-squared values, and progress messages.

Fitting Progress Tracking and Exposure:

• Added new properties to the Python backend logic (fitting.py) and QML interfaces to track and expose fitting progress, including current iteration, interim chi-squared, reduced chi-squared, progress messages, and preview parameter values. These are now available in both the backend (analysis.py) and frontend (BackendWrapper.qml).

• Implemented a mechanism for the fitting worker thread to emit detailed progress updates via a new progressDetail signal, which is handled in the backend to update the fitting state and propagate changes to the UI.

User Interface Enhancements:

• Updated the status bar to display live fitting progress, including the current iteration and reduced chi-squared, with fallback animation when interim updates are not available.

• Ensured that fit progress and results dialogs are properly managed and dismissed on both acceptance and rejection, improving UI consistency.

• Refactored the loading and placement of the FitStatusDialog component to avoid redundant instantiation and ensure it's available at the correct UI level.

Fitting Operation Robustness and State Management:

• Improved state management by clearing progress information on fit completion, cancellation, or failure, ensuring the UI always reflects the current fitting state.

• Enhanced error handling for user-initiated fit cancellation, providing clear messaging and preventing unnecessary error dialogs.

[rozyczko]

This needs interim_updates in core to be merged first