[US-01] Setting ships somewhere on the board

Description

Implements ship placement functionality for the Battleship game as described in issue #1.

Changes

• Created core model classes: Board, Ship, Coordinate, Direction, Player, Game
• Implemented ship placement validation with boundary checks and overlap prevention
• Added comprehensive test coverage for all ship placement scenarios
• Followed the planned layered architecture with model, service, and view packages

Features Implemented

• 10x10 game board for each player
• Standard fleet: Carrier (5), Battleship (4), Cruiser (3), Submarine (3), Destroyer (2)
• Ship placement validation: boundaries, overlaps, straight placement only
• Error handling for invalid placements
• Board state management and ship tracking

Acceptance Criteria Verified

✅ If a ship is placed outside the board, the action should not succeed and an error or similar feedback should appear.

• Implemented boundary validation in Board.validateShipPlacement()
• Tested in BoardTest.testPlaceShipOutsideBoundariesHorizontal() and BoardTest.testPlaceShipOutsideBoundariesVertical()

✅ If two ships end up on the same squares, the later placement should not overwrite the earlier one.

• Implemented overlap detection in Board.validateShipPlacement()
• Tested in BoardTest.testPlaceShipOverlap()

✅ When all ships have been placed validly, the board can be considered ready and hidden for the opponent.

• Implemented Board.allShipsPlaced() method
• Standard fleet management with Board.getStandardFleet()

Technical Details

• Java 21 with Maven build system
• JUnit 5 testing framework
• Layered architecture following MVC pattern
• Comprehensive test coverage with 70%+ code coverage requirement

Closes #1