[US-01] Place fleet on a concealed board

Description

Implements ship placement functionality for Battleship game according to Issue #1 requirements.

Changes

• Created complete Java application with GUI interface
• Implemented ship placement validation and game state management
• Added comprehensive test suite with 51 tests
• All acceptance criteria validated and passing

Requirements Implemented

✅ Provide a 10×10 grid per player ✅ Provide a standard fleet with ship lengths: Carrier (5), Battleship (4), Destroyer (3), Submarine (3), Patrol Boat (2) ✅ Allow placement horizontally or vertically; reject diagonal, overlapping, or out-of-bounds placements ✅ Keep each player's ship locations hidden from the opponent

Acceptance Criteria Validated

✅ Given a ship partly outside the grid, when placement is attempted, then the system rejects it with an error and no placement occurs ✅ Given two ships sharing any square, when the second is placed, then placement is rejected and existing ships remain unchanged ✅ Given a valid layout, when all ships are placed, then the board is marked ready and remains hidden from the opponent

Technical Details

• Pipeline: #8010 ✅ SUCCESS
• Tests: 51/51 passing (100% success rate)
• Architecture: Layered (model, controller, service, util, view)
• Tech Stack: Java 21, Maven, JUnit 5

Closes #1