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/Setup/DatabaseSetup.cs

@@ -0,0 +1,90 @@
+using EchoHub.Core.Constants;
+using EchoHub.Core.Models;
+using EchoHub.Server.Data;
+using Microsoft.EntityFrameworkCore;
+
+namespace EchoHub.Server.Setup;
+
+public static class DatabaseSetup
+{
+    public static async Task InitializeAsync(IServiceProvider services)
+    {
+        using var scope = services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<EchoHubDbContext>();
+        var logger = scope.ServiceProvider.GetRequiredService<ILoggerFactory>()
+            .CreateLogger("EchoHub.Server.Setup.DatabaseSetup");
+
+        await MigrateAsync(db, logger);
+        await SeedDefaultChannelAsync(db, logger);
+    }
+
+    private static async Task MigrateAsync(EchoHubDbContext db, ILogger logger)
+    {
+        try
+        {
+            if (await db.Database.CanConnectAsync())
+                await HandleLegacyDatabaseAsync(db, logger);
+
+            await db.Database.MigrateAsync();
+            logger.LogInformation("Database migrated successfully.");
+        }
+        catch (Exception ex)
+        {
+            logger.LogError(ex, "Database migration failed.");
+            throw;
+        }
+    }
+
+    private static async Task HandleLegacyDatabaseAsync(EchoHubDbContext db, ILogger logger)
+    {
+        var conn = db.Database.GetDbConnection();
+        await conn.OpenAsync();
+
+        using var cmd = conn.CreateCommand();
+        cmd.CommandText = "SELECT count(*) FROM sqlite_master WHERE type='table' AND name='__EFMigrationsHistory'";
+        var hasMigrationTable = Convert.ToInt64(await cmd.ExecuteScalarAsync()) > 0;
+
+        if (!hasMigrationTable)
+        {
+            cmd.CommandText = "SELECT count(*) FROM sqlite_master WHERE type='table' AND name='Users'";
+            var hasLegacyTables = Convert.ToInt64(await cmd.ExecuteScalarAsync()) > 0;
+
+            if (hasLegacyTables)
+            {
+                var dbPath = conn.DataSource;
+                await conn.CloseAsync();
+
+                if (!string.IsNullOrEmpty(dbPath) && File.Exists(dbPath))
+                {
+                    var timestamp = DateTime.Now.ToString("yyyyMMdd_HHmmss");
+                    var backupPath = $"{dbPath}.legacy_{timestamp}";
+                    File.Copy(dbPath, backupPath, overwrite: false);
+                    logger.LogWarning("Legacy database backed up to '{BackupPath}'.", backupPath);
+                }
+
+                await db.Database.EnsureDeletedAsync();
+                logger.LogWarning("Legacy database removed. A new database will be created with migration support.");
+                return;
+            }
+        }
+
+        await conn.CloseAsync();
+    }
+
+    private static async Task SeedDefaultChannelAsync(EchoHubDbContext db, ILogger logger)
+    {
+        if (await db.Channels.AnyAsync(c => c.Name == HubConstants.DefaultChannel))
+            return;
+
+        db.Channels.Add(new Channel
+        {
+            Id = Guid.NewGuid(),
+            Name = HubConstants.DefaultChannel,
+            Topic = "General discussion",
+            CreatedByUserId = Guid.Empty,
+        });
+
+        await db.SaveChangesAsync();
+        logger.LogInformation("Default channel '{Channel}' created.", HubConstants.DefaultChannel);
+    }
+}