feat: complete client-server architecture refactoring

Server:
- Split into views, routes, helpers, models modules
- Merged /ws/talk and /ws/update into single /ws/chat endpoint
- Replaced polling with push-based broadcast model
- Added username uniqueness validation on connect
- Fixed run_server arguments bug (workers parameter)
- Removed deprecated loop argument from Sanic listeners
- Replaced datetime.utcnow() with timezone-aware datetime.now(timezone.utc)

Client:
- Rewrote client as single-file module
- Migrated from websocket-client to websockets (asyncio)
- Fixed websocket-client conflict with asyncio event loop on Windows
- Added progress indicators for key generation, exchange, connection
- Added animated 3D spinning cube in UI
- Updated RSA key from 512 to 2048 bits

CLI:
- Removed unnecessary asyncio.run() wrapper
- Simplified entry point

cmd_chat/server/models.py

@@ -1,5 +1,31 @@
-from pydantic import BaseModel 
+from dataclasses import dataclass, field
+from uuid import uuid4
+from datetime import datetime
+from typing import Optional
 
-class Message(BaseModel):
 
-    message: str 
+@dataclass
+class Message:
+    id: str = field(default_factory=lambda: str(uuid4()))
+    text: str = ""
+    timestamp: str = field(default_factory=lambda: datetime.utcnow().isoformat())
+    user_ip: str = ""
+    username: str = ""
+
+
+@dataclass
+class UserSession:
+    user_id: str
+    ip: str
+    username: str = "unknown"
+    fernet_key: Optional[bytes] = None
+    created_at: str = field(default_factory=lambda: datetime.utcnow().isoformat())
+    last_activity: str = field(default_factory=lambda: datetime.utcnow().isoformat())
+    active: bool = True
+
+    def update_activity(self):
+        self.last_activity = datetime.utcnow().isoformat()
+
+    def is_stale(self, timeout_seconds: int = 3600) -> bool:
+        last = datetime.fromisoformat(self.last_activity)
+        return (datetime.utcnow() - last).total_seconds() > timeout_seconds