feat: implement HouseRobbing DP solution

[bushidocodes]

Summary

• Adds HouseRobbing, a final static utility class in edu.gwu.csci6212, implementing the circular house-robber DP problem
• Reduces the circular problem to two linear subproblems (exclude last house / exclude first house), each solved with the standard dp[i] = max(dp[i-1], dp[i-2] + houses[i]) recurrence
• Validates input (null, empty, negative values) with IllegalArgumentException, matching the style of CoinPickingGame and MinimumStepsChessKnight

Test plan

• Rejects null array
• Rejects empty array
• Rejects negative house value
• Single house returns its value
• Two houses returns the larger
• Two identical houses returns that value
• Assignment example 1: [2,3,2] → 3
• Assignment example 2: [1,2,3,1] → 4
• Greedy-fail case: [6,1,9,1,6] → 15 (naive every-other greedy would wrongly claim 6+9+6=21, violating the circular adjacency)
• All-zeroes array returns 0
• Larger circular case: [2,7,9,3,1] → 11

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