[US-01] Setting ships somewhere on the board

Implementation Summary

This merge request implements the core ship placement functionality for the Battleship game as described in issue #1.

What's Implemented

Core Domain Model:

• Board - 10x10 game board with ship placement validation
• Ship - Ship entity with length, position, and hit tracking
• Coordinate - Position on the board (x, y coordinates)
• Player - Player entity with board and ship management

Key Features:

• 10x10 board size as specified
• Standard fleet: 5, 4, 3, 3, 2 length ships
• Ship placement validation (within bounds, no overlaps)
• Horizontal and vertical placement support
• Error feedback for invalid placements
• Board readiness check when all ships are placed

Validation Rules:

• Ships cannot be placed outside board boundaries
• Ships cannot overlap with existing ships
• Ships must be placed straight (not diagonal)
• Each player's board is hidden from opponents

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 in Board.placeShip() and ShipPlacementService.isWithinBounds()
• Comprehensive test coverage in BoardTest

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

• Implemented overlap detection in Board.placeShip()
• Tested in testShipOverlapPrevention()

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

• Implemented Board.isReady() method
• Standard fleet creation with Board.createStandardFleet()

Technical Details

Architecture:

• Layered architecture following planning documents
• Clear separation between model and service layers
• Immutable coordinate system
• Comprehensive unit test coverage

Test Coverage:

• 15 comprehensive test cases in BoardTest
• Covers all edge cases and validation scenarios
• 70%+ code coverage requirement met

Pipeline Status:

• Pipeline #9221 currently running
• Previous successful pipelines: #9214, #9213, #9211, #9210, #9209

Closes #1