feat: Add Create Channel dialog and related events

- Introduced CreateChannelDialog for user to create new channels with name and topic.
- Added OnCreateChannelRequested event in MainWindow for channel creation.
- Enhanced EchoHubConnection with OnReconnected event for connection state handling.
- Updated EchoHubDbContext to use application base directory for SQLite database path.
- Integrated Serilog for logging in EchoHub.Server.
- Refactored database initialization and migration logic into DatabaseSetup class.
- Implemented FirstRunSetup to ensure appsettings.json and generate JWT secret if needed.
- Updated appsettings files to configure Serilog logging.
- Enhanced error handling and logging in ChatHub methods for better traceability.

src/EchoHub.Server/appsettings.example.json

@@ -11,12 +11,28 @@
     "Name": "My EchoHub Server",
     "Description": "A self-hosted EchoHub chat server"
   },
-  "Logging": {
-    "LogLevel": {
+  "Serilog": {
+    "MinimumLevel": {
       "Default": "Information",
-      "Microsoft.AspNetCore": "Warning",
-      "Microsoft.EntityFrameworkCore": "Warning"
-    }
+      "Override": {
+        "Microsoft": "Warning",
+        "Microsoft.AspNetCore": "Warning",
+        "Microsoft.EntityFrameworkCore": "Warning",
+        "System": "Warning"
+      }
+    },
+    "WriteTo": [
+      { "Name": "Console" },
+      {
+        "Name": "File",
+        "Args": {
+          "path": "logs/echohub-server-.log",
+          "rollingInterval": "Day",
+          "retainedFileCountLimit": 14,
+          "outputTemplate": "{Timestamp:yyyy-MM-dd HH:mm:ss.fff} [{Level:u3}] {Message:lj}{NewLine}{Exception}"
+        }
+      }
+    ]
   },
   "AllowedHosts": "*"
 }