Add Median of Two Sorted Arrays solution in Java (#359)

[maitriupadhyay03-cell]

Closes #359

Summary

This PR adds a Java solution for the Median of Two Sorted Arrays problem.

Approach

Binary search on the smaller array to find the correct partition point:

• Ensure nums1 is the smaller array
• • Use binary search to find partition such that all elements in the left half ≤ all elements in the right half
• • Compute median based on whether total length is odd or even

Complexity

• Time: O(log(min(m, n)))
• • Space: O(1)

Test Cases

• [1, 3] and [2] → 2.0
• • [1, 2] and [3, 4] → 2.5
• • [] and [1] → 1.0
• • [0, 0] and [0, 0] → 0.0