Enhance alphaBetaMasses with velocity-dependent final mass computation

[AstroEloy]

This update extends alphaBetaMasses by supporting the full alpha-beta final-mass solution when both initial and final velocities are provided. The previous asymptotic approximation is retained for backward compatibility when velocity information is unavailable.

Additional improvements include:

• Input validation for alpha, beta, mu, density, drag parameter, shape coefficient, and velocities.
• Optional verbose output summarizing the adopted parameters and resulting mass estimates.
• Expanded documentation.

[dvida]

Thanks for the PR — the velocity-dependent final-mass extension is a useful addition and the underlying math is correct (it's the standard Gritsevich dimensionless mass equation, with the old exp(-beta/(1-mu)) recovered as the v_end → 0 limit). The input validation is also a nice touch. A few things to fix before merge:

1. Duplicate function definition (blocking). The new alphaBetaMasses is appended after the existing one rather than replacing it. The file now has two functions with the same name (old at lines ~456–487, new right after). Python silently uses the last definition, so the old one becomes dead code. Please delete the original def alphaBetaMasses(...) block and keep only the new version. As-is, this also leaves two conflicting docstrings (gamma described as "Drag coefficient (2*drag factor)" in the old one vs. "Γ = C_D/2" in the new one).

2. Feature isn't wired into the CLI. The only callers are in the __main__ block (lines ~612 and ~614), and they don't pass vel_init/vel_end — so the new full solution is never exercised by the script itself, only via direct import. Since v_init is already available (line ~608) and the trajectory has the final velocity, please pass them through so the CLI actually uses the new path (or note explicitly that it's library-only).

3. Minor style. Trailing whitespace on several blank lines (docstring opener, before if verbose, etc.), and add a second blank line before the def per PEP8.

Once the duplicate is removed and the velocities are plumbed into the main block, this is good to go.