Encapsulate utility functions into CloudRemoval class for better code organization

[Copilot]

This PR refactors the cloud_removal.py module to improve code organization by moving standalone utility functions into the CloudRemoval class as static methods.

Problem

The original code had three utility functions defined as standalone functions outside the class:

• set_seed(seed=4096) - for setting random seeds for reproducibility
• thres_21(L, tau, M, N, B) - for threshold computation in the optimization algorithm
• deal_real_data_for_gdd(Noisy) - for preprocessing data for the GDD network

This created a mixed code structure where cloud removal functionality was split between the CloudRemoval class and global utility functions, making the codebase less organized and harder to maintain.

Solution

Moved all three utility functions into the CloudRemoval class as static methods:

class CloudRemoval():
    # ... existing methods ...
    
    @staticmethod
    def set_seed(seed=4096):
        # ... implementation unchanged ...
    
    @staticmethod
    def thres_21(L, tau, M, N, B):
        # ... implementation unchanged ...
    
    @staticmethod
    def deal_real_data_for_gdd(Noisy):
        # ... implementation unchanged ...

Updated all internal function calls to use the class methods:

• set_seed() → CloudRemoval.set_seed()
• thres_21(L, tau, M, N, B) → CloudRemoval.thres_21(L, tau, M, N, B)

Benefits

1. Complete encapsulation - All cloud removal functionality is now self-contained within the CloudRemoval class
2. Cleaner namespace - No global utility functions cluttering the module scope
3. Better organization - Clear logical grouping of related functionality
4. Improved maintainability - Easier to understand relationships between functions
5. Backward compatibility - No breaking changes to the public API; main.py continues to work unchanged

Testing

• ✅ Syntax verification confirms the code compiles correctly
• ✅ AST analysis confirms proper class structure with all methods properly encapsulated
• ✅ No standalone functions remain outside the class
• ✅ All function calls have been correctly updated to use class methods

The refactoring achieves the goal of making the cloud removal logic clearer and more organized while maintaining full backward compatibility.

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