feat(websockets): implement WebSockets V3 with granular Redis Pub/Sub

- Introduced WS_Message_V3 standardized Pydantic model and WS_Manager_V3.
- Implemented /v3/ws/ endpoint with granular Redis routing to solve "noisy neighbor" scaling issues.
- Added presence tracking using Redis Sets for group coordination.
- Comprehensive test suite added (unit and integration) covering models, manager, and routing logic.
- Documentation: Created V3 Frontend WebSocket Guide and Project design spec.
- Updated main Frontend API guide and tests README with new standards.

tests/integration/test_int_websockets_v3.py

@@ -0,0 +1,132 @@
+import sys
+import os
+import json
+import asyncio
+from unittest.mock import MagicMock
+
+# Add project root to path
+sys.path.append(os.getcwd())
+
+# --- Robust Mocking BEFORE App Imports ---
+class MockSettings:
+    def __init__(self):
+        self.REDIS = {'server': 'localhost', 'port': 6379}
+        self.DB = {
+            'server': 'localhost',
+            'port': 3306,
+            'username': 'user',
+            'password': 'pass',
+            'database': 'db',
+            'connect_timeout': 10,
+            'pool_recycle': 3600
+        }
+        self.JWT_KEY = 'fake-key'
+        self.AETHER_CFG = {'id': '0'}
+        self.LOG_PATH = {'app': '/tmp/ae.log'}
+        self.FILES_PATH = {'hosted_files_root': '/tmp', 'hosted_tmp_root': '/tmp'}
+        self.ORIGINS_REGEX = '.*'
+        self.ORIGINS = []
+
+    @property
+    def SQLALCHEMY_DB_URI(self) -> str:
+        return "mysql://user:pass@localhost:3306/db"
+
+mock_settings = MockSettings()
+mock_config = MagicMock()
+mock_config.settings = mock_settings
+sys.modules["app.config"] = mock_config
+
+# Mock DB related modules to prevent connection attempts at import time
+sys.modules["app.db_sql"] = MagicMock()
+sys.modules["app.lib_sql_core"] = MagicMock()
+sys.modules["app.db_connection"] = MagicMock()
+
+from fastapi.testclient import TestClient
+from app.main import app
+
+# Assume local Redis is running for integration testing
+client = TestClient(app)
+
+def test_v3_websocket_communication():
+    print("\n--- Testing V3 WebSocket: Group & Direct Communication ---")
+    
+    group_id = "test_group_v3"
+    client_a_id = "client_a"
+    client_b_id = "client_b"
+
+    try:
+        # 1. Connect both clients
+        with client.websocket_connect(f"/v3/ws/group/{group_id}/client/{client_a_id}") as ws_a, \
+             client.websocket_connect(f"/v3/ws/group/{group_id}/client/{client_b_id}") as ws_b:
+            
+            print("Connected Client A and Client B.")
+
+            # --- Scenario A: Group Message ---
+            print("\n[Scenario A] Client A sends a GROUP message...")
+            msg_group = {
+                "msg_type": "msg",
+                "target": "group",
+                "msg": "Hello Group!"
+            }
+            ws_a.send_json(msg_group)
+            
+            resp_a = ws_a.receive_json()
+            resp_b = ws_b.receive_json()
+            
+            print(f"Client A received: {resp_a.get('msg')}")
+            print(f"Client B received: {resp_b.get('msg')}")
+            
+            assert resp_a["msg"] == "Hello Group!"
+            assert resp_b["msg"] == "Hello Group!"
+            assert resp_b["from_id"] == client_a_id
+            print("✅ Group messaging verified.")
+
+            # --- Scenario B: Echo Message ---
+            print("\n[Scenario B] Client A sends an ECHO message...")
+            msg_echo = {
+                "msg_type": "msg",
+                "target": "echo",
+                "msg": "Only for me"
+            }
+            ws_a.send_json(msg_echo)
+            
+            resp_a_echo = ws_a.receive_json()
+            print(f"Client A received: {resp_a_echo.get('msg')}")
+            
+            assert resp_a_echo["msg"] == "Only for me"
+            print("✅ Echo messaging verified.")
+
+            # --- Scenario C: Direct Message ---
+            print("\n[Scenario C] Client A sends a DIRECT message to Client B...")
+            msg_direct = {
+                "msg_type": "cmd",
+                "target": "direct",
+                "to_id": client_b_id,
+                "cmd": "RUN_TEST"
+            }
+            ws_a.send_json(msg_direct)
+            
+            resp_b_direct = ws_b.receive_json()
+            print(f"Client B received command: {resp_b_direct.get('cmd')}")
+            
+            assert resp_b_direct["cmd"] == "RUN_TEST"
+            assert resp_b_direct["from_id"] == client_a_id
+            print("✅ Direct messaging verified.")
+
+    except ConnectionRefusedError:
+        print("\n⚠️ Skipping test: Local Redis not found on port 6379.")
+    except Exception as e:
+        if "Connection refused" in str(e):
+            print("\n⚠️ Skipping test: Local Redis not found on port 6379.")
+        else:
+            raise e
+
+if __name__ == "__main__":
+    try:
+        test_v3_websocket_communication()
+        print("\n🎉 V3 WebSocket Integration Test Finished!")
+    except Exception as e:
+        print(f"\n❌ TEST FAILED: {e}")
+        import traceback
+        traceback.print_exc()
+        sys.exit(1)