v3.0.0: V3 features, server refactoring, and documentation overhaul

- Extract WebSocket handlers from main.py into handlers.py
- Add V3 feature docs (dealer rotation, dealing animation, round end reveal,
  column pair celebration, final turn urgency, opponent thinking, score tallying,
  card hover/selection, knock early drama, column pair indicator, swap animation
  improvements, draw source distinction, card value tooltips, active rules context,
  discard pile history, realistic card sounds)
- Add V3 refactoring docs (ai.py, main.py/game.py, misc improvements)
- Add installation guide with Docker, systemd, and nginx setup
- Add helper scripts (install.sh, dev-server.sh, docker-build.sh)
- Add animation flow diagrams documentation
- Add test files for handlers, rooms, and V3 features
- Add e2e test specs for V3 features
- Update README with complete project structure and current tech stack
- Update CLAUDE.md with full architecture tree and server layer descriptions
- Update .env.example to reflect PostgreSQL (remove SQLite references)
- Update .gitignore to exclude virtualenv files, .claude/, and .db files
- Remove tracked virtualenv files (bin/, lib64, pyvenv.cfg)
- Remove obsolete game_log.py (SQLite) and games.db

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/room.py

@@ -254,12 +254,13 @@ class RoomManager:
         """Initialize an empty room manager."""
         self.rooms: dict[str, Room] = {}
 
-    def _generate_code(self) -> str:
+    def _generate_code(self, max_attempts: int = 100) -> str:
         """Generate a unique 4-letter room code."""
-        while True:
+        for _ in range(max_attempts):
             code = "".join(random.choices(string.ascii_uppercase, k=4))
             if code not in self.rooms:
                 return code
+        raise RuntimeError("Could not generate unique room code")
 
     def create_room(self) -> Room:
         """