1.2.0 fixes

[rozyczko]

This pull request introduces several improvements and fixes across the EasyReflectometry application, focusing on experiment loading, model/parameter handling, fitting result reporting, and user interface enhancements. The most notable changes include automatic synchronization of q-range limits when loading experiments, improved calculation and reporting of fit statistics, and UI updates to better reflect application state and actions.

Key changes:

Experiment and Model Handling

• Added logic to synchronize the model's q_max value with the largest q value from loaded experiments. This ensures that model limits reflect the data and emits a new qRangeUpdated signal when the q-range changes. This affects how experiments are loaded and signals are propagated throughout the application.
• Updated the Models class to fetch models dynamically from the project library, ensuring the model list is always up-to-date.

Fitting Results and Parameter Display

• Improved the calculation of fit statistics: fit_n_pars now reports the global number of refined parameters (not a sum), and fit_chi2 now returns the reduced chi-squared (chi2 per degree of freedom) for multi-fit scenarios, providing more accurate and meaningful fit quality metrics.
• Refined parameter display logic so that for layer parameters, the assembly name is shown instead of the layer name, making the Analysis parameters table reflect changes made in the Model Editor.

User Interface and Signal Connections

• Added a prominent "Start/Cancel Fitting" button to the Analysis page sidebar, reflecting fitting state and providing a clear action for users.
• Improved signal connections so that q-range updates, parameter changes, and experiment changes more reliably trigger UI updates and status bar refreshes, ensuring the interface stays in sync with backend changes.

Maintenance and Copyright

• Updated copyright years to 2026 across Python and QML files.

These changes collectively improve data integrity, result reporting, and the responsiveness of the user interface to changes in the application's state.