[US-03] Track ship damage, announce sunk, and end the game

Description

Implements ship damage tracking, sunk announcements, and game ending functionality for Battleship game.

Changes

• Added ship damage tracking with hit recording
• Implemented ship sunk detection and announcements
• Added game ending logic when all ships are sunk
• Implemented new game functionality
• Added comprehensive test coverage

Requirements Implemented

✅ Track hits per ship and determine when all squares of a ship are hit ✅ Upon completion, announce the ship as 'sunk' ✅ When all ships of a player are sunk, declare victory for the opponent and disable further input ✅ Provide New Game to start a fresh match

Acceptance Criteria Validated

✅ Given the last undamaged square of a ship is hit, when the result is processed, then that ship is announced 'sunk' ✅ Given the final enemy ship is sunk, when the board updates, then the match ends, the winner is indicated, and no further shots are allowed ✅ Given a finished match, when New Game is chosen, then both boards reset to covered, unplaced state

Technical Details

• Added Ship.isSunk() method to detect when all positions are hit
• Enhanced Game.processShot() to handle sunk ships and game ending
• Added Player.hasLost() to check if all ships are sunk
• Implemented Game.newGame() for reset functionality
• Comprehensive test coverage in ShipTest.java and GameTest.java

Closes #3