Add RC2001 deceleration correction and calcMass support

[AstroEloy]

This PR improves the implementation of the luminous efficiency model from ReVelle & Ceplecha (2001) and its application in photometric mass estimation.

Changes:

• Added support for the velocity-dependent deceleration correction term described by ReVelle & Ceplecha (2001).
• Extended luminousEfficiency() with an optional v_init argument representing the pre-atmospheric velocity.
• Implemented the ReVelle & Ceplecha (2001) deceleration correction using the velocity difference (v_init - vel).
• For v_init = vel, the deceleration correction is set to zero.
• Velocity values larger than v_init are treated as physically inconsistent and will cause the logarithm evaluation to fail.
• Added documentation describing the assumptions and validity limits of the deceleration correction term.

Photometric mass calculation (calcMass):

• Added support for passing a pre-atmospheric velocity through the new v_init argument.
• Added three operating modes for the ReVelle & Ceplecha deceleration correction:
  • v_init=None: do not apply the correction (it translates into -1 for luminousEfficiency()).
  • v_init=-1: use the maximum value of the supplied velocity profile as the pre-atmospheric velocity.
  • v_init>0: use the user-provided pre-atmospheric velocity.
• Updated the documentation to clarify the expected use of velocity profiles and the assumptions behind the automatic pre-atmospheric velocity selection.

Velocity-dependent mass integration:

• Fixed the treatment of variable velocity when a constant luminous efficiency is supplied.
• The mass is now computed using
  M = \frac{2}{\tau}\int \frac{I}{v^2},dt
  when a velocity profile is provided, instead of incorrectly assuming constant velocity.

Input validation:

• Added validation that time and mag_abs have identical lengths.
• Added validation that velocity arrays have the same length as the photometric measurements.
• Added validation for lum_eff_mass, which must be either:
  • -1 (self-consistent iteration), or
  • a non-negative mass value.

Self-consistent luminous efficiency iteration:

• Added a warning message when the luminous-efficiency self-consistency iteration fails to converge after the maximum number of iterations.
• Improved documentation of the convergence procedure and mass iteration workflow.

Documentation:

• Expanded the documentation of calcMass() and luminousEfficiency().
• Clarified the distinction between constant and velocity-dependent luminous efficiency calculations.
• Added documentation for the new pre-atmospheric velocity handling and associated assumptions.