Relicense project under GPL-3.0-or-later

Replaces the previous MIT license with GPL-3.0-or-later. Adds the full
GPL-3.0 license text at LICENSE, updates pyproject.toml metadata and
classifier, updates the README, and adds SPDX-License-Identifier headers
to all first-party server Python and client JavaScript sources.
Third-party anime.min.js is left untouched.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/services/__init__.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
 """Services package for Golf game V2 business logic."""
 
 from .recovery_service import RecoveryService, RecoveryResult

server/services/admin_service.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
 """
 Admin service for Golf game.
 

server/services/auth_service.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
 """
 Authentication service for Golf game.
 

server/services/email_service.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
 """
 Email service for Golf game authentication.
 

server/services/game_logger.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
 """
 PostgreSQL-backed game logging for AI decision analysis.
 

server/services/matchmaking.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
 """
 Matchmaking service for public skill-based games.
 

server/services/ratelimit.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
 """
 Redis-based rate limiter service.
 

server/services/rating_service.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
 """
 Glicko-2 rating service for Golf game matchmaking.
 

server/services/recovery_service.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
 """
 Game recovery service for rebuilding active games from event store.
 

server/services/replay_service.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
 """
 Replay service for Golf game.
 

server/services/spectator.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
 """
 Spectator manager for Golf game.
 

server/services/stats_service.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
 """
 Stats service for Golf game leaderboards and achievements.