A quantum computer can never break a single Bitcoin key. Final answer.
Lindblad master equation
(The equation for self-decoherence.)
Γ_self ≈ γ N²
Even with perfect isolation (γ → 10⁻⁸ s⁻¹),
N² × 10⁻⁸ × 3600 ≪ 1 to stay coherent 1 hour
→ N ≲ 170 qubits max
This means that a perfect, maximum-scale QC with perfect engineering is more than an order of magnitude short of cracking your stack.
Tick tock, next block.