Harden vendored f90wrap path for Qt/QGIS compatibility

[sunt05]

Summary

Improves the vendored f90wrap code generation to ensure Qt/QGIS compatibility by hardening the module path handling and removing conflicting SIGINT handler modifications.

Changes

• Vendor f2py_f90wrap.py with Qt-safe error handling
• Remove SIGINT handler conflicts with Qt signal handlers
• Add comprehensive Qt integration tests for Windows QGIS CI
• Improve f90wrap path robustness in module loading

Quick Reproduction

from supy import SUEWSSimulation

sim = SUEWSSimulation.from_sample_data()

# Set z < zdm_in via config to trigger crash
sim.update_config({
    "sites": {
        "properties": {
            "z": {"value": 5.0},
            "zdm_in": {"value": 15.0}
        }
    }
})

# This triggers the error
sim.run(end_date=sim.forcing.index[287])

Fixes #1035

[sunt05]

Additional Fix: Early Return for Fatal Errors

Added RETURN after ErrorHint(32) in cal_Stab subroutine (suews_phys_atmmoiststab.f95) to prevent LOG(negative) crash.

Before: ErrorHint set the error state, but execution continued to LOG(zzd/z0m) which crashed on negative values.

After: Subroutine returns immediately after setting error state, allowing Python to catch SUEWSKernelError.

This completes the fix for #1035 - the SIGINT handler removal ensures Qt compatibility, and this change ensures fatal errors exit cleanly before hitting undefined math operations.