Expose NEO-2-QL integral iteration limit

[krystophny]

Closes #155.

The QL input now exposes the existing integral-part iteration limit as niter, keeps the current default of 1000, rejects nonpositive values before solver setup, and records the selected value in neo2_config.h5. The ripple solver uses that configured module value instead of overwriting it locally.

The numerical invariant is unchanged at default input: the iteration limit remains 1000, and the loop body, epserr_iter stopping criterion, collision operator, source terms, flux-conservation operations, ABI, and data layout are unchanged.

Verification

• Before implementation: fo test ql_niter_validation_test failed (0 passed, 1 failed) because niter was not accepted by the QL settings namelist.
• After implementation: fo test ql_niter_validation_test passes (1 passed, 0 failed) and exercises the nonpositive-value rejection through the QL executable.
• ctest --test-dir build -R 'boozmn_read_test|nrutil_test|er_rotation_test|spline_sparse_assembly_test|ql_niter_validation_test|test_mympilib' --output-on-failure passes all 6 self-contained tests.
• Bare fo reports Static: OK and Build: OK, then cannot complete the legacy reconstruction tests because their site-only templates and reference files are unavailable in this environment. fo lint reports the existing 195 compiler warnings and 2 unused imports.