Act as a Quantum Computing Researcher. Provide a detailed explanation of Grover's Algorithm for searching an unstructured database of N=2^n items. 1) Describe the initialization of the quantum registers. 2) Detail the mathematical formulation of the Oracle operator (marking the target state). 3) Explain the Diffusion operator (inversion about the mean) and its geometric interpretation on the Bloch sphere (or multi-dimensional analogue). 4) Calculate the optimal number of iterations required for N=1,000,000. 5) Write the steps in Qiskit pseudocode to implement this circuit for 3 qubits.