Phase Transition of the Optico-Hydrodynamic Vacuum (OHV) as a Dynamic Resolution of Black Hole Singularity

General Relativity (GR) is extremely successful on macroscopic scales, yet it predicts unphysical singularities at the centers of black holes. Within the phenomenological model of the Optico-Hydrodynamic Vacuum (OHV), gravity is treated not as metric curvature but as a local gradient of an effective vacuum viscosity eta_grav(r) = GM / (r * c^2). In the weak-field limit, this dissipation reproduces the standard gravitational redshift Delta E / E approx -GM / (r * c^2) observed in Solar-System experiments, without any free factors. We show that the saturation limit of the medium (eta = 1, i.e., 100% dissipation) triggers a vacuum phase transition (crystallisation), halting collapse at the critical radius r_OHV = GM / c^2 = r_S / 2. Although the physical boundary of the Black Star lies at r_S / 2, the extreme refractive-index gradient of the viscous vacuum acts as a gravitational super-lens, bending photon trajectories so severely that the observed optical shadow matches the dimensions measured by the Event Horizon Telescope for M87* and Sgr A*. This eliminates the mathematical singularity and produces a macroscopic compact object — the Black Star — with a mass-dependent finite density rho_OHV = 3 * c^6 / (4 * pi * G^3 * M^2). Since baryonic matter is itself a saturated phase of the vacuum substrate in the OHV framework, setting rho_OHV = rho_nucl as a self-consistency requirement analytically predicts a critical mass for black hole formation of M_crit approx 25.4 Solar Masses, consistent with the dominant population of stellar-mass black holes detected by LIGO/Virgo. The model further predicts a frequency-dependent dispersion of gravitational redshift in ultra-strong fields, absent in standard GR.