Refactor EchoHub solution structure and remove unused components

- Deleted EchoHub.slnx and related project files for EchoHub.Web and EchoHub.Api.
- Removed ServerDirectoryDbContext, ServerDirectoryService, and related extensions and DTOs.
- Updated CommandHandler and Program.cs in EchoHub.Client to handle URL sending instead of file downloading.
- Added SendUrlRequest DTO and corresponding API endpoint in ChannelsController for handling URL uploads.
- Implemented database migration support in EchoHub.Server with initial migration setup.
- Adjusted Program.cs to include HTTP client configuration for image downloading.
- Cleaned up unnecessary files and references to streamline the project.

src/EchoHub.Server/Program.cs

@@ -73,6 +73,11 @@ builder.Services.AddSingleton<JwtTokenService>();
 builder.Services.AddSingleton<PresenceTracker>();
 builder.Services.AddSingleton<ImageToAsciiService>();
 builder.Services.AddSingleton<FileStorageService>();
+builder.Services.AddHttpClient("ImageDownload", client =>
+{
+    client.Timeout = TimeSpan.FromSeconds(15);
+    client.MaxResponseContentBufferSize = 10 * 1024 * 1024; // 10 MB
+});
 
 // ── Rate Limiting ────────────────────────────────────────────────────────────
 builder.Services.AddRateLimiter(options =>
@@ -125,8 +130,64 @@ var app = builder.Build();
 using (var scope = app.Services.CreateScope())
 {
     var db = scope.ServiceProvider.GetRequiredService<EchoHubDbContext>();
-    await db.Database.EnsureCreatedAsync();
+    var logger = scope.ServiceProvider.GetRequiredService<ILogger<Program>>();
 
+    try
+    {
+        // If the DB was created by EnsureCreated (no __EFMigrationsHistory table),
+        // back it up and recreate so MigrateAsync can manage the schema properly.
+        if (await db.Database.CanConnectAsync())
+        {
+            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();
+
+                    // Back up the legacy DB file before deleting
+                    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.");
+                }
+                else
+                {
+                    await conn.CloseAsync();
+                }
+            }
+            else
+            {
+                await conn.CloseAsync();
+            }
+        }
+
+        await db.Database.MigrateAsync();
+        logger.LogInformation("Database migrated successfully.");
+    }
+    catch (Exception ex)
+    {
+        logger.LogError(ex, "Database migration failed.");
+        throw;
+    }
+
+    // Seed the default channel if it doesn't exist
     if (!await db.Channels.AnyAsync(c => c.Name == HubConstants.DefaultChannel))
     {
         db.Channels.Add(new Channel
@@ -138,6 +199,7 @@ using (var scope = app.Services.CreateScope())
         });
 
         await db.SaveChangesAsync();
+        logger.LogInformation("Default channel '{Channel}' created.", HubConstants.DefaultChannel);
     }
 }