Refactor and update various components of EchoHub.Server

- Updated launchSettings.json for consistency.
- Refactored FileValidationHelper to improve image validation logic.
- Enhanced ServerDirectoryService for better connection handling and user count updates.
- Improved DatabaseSetup for legacy database handling and seeding default channels.
- Refined FirstRunSetup to ensure JWT secret generation.
- Removed appsettings.Development.json as it is no longer needed.
- Updated EchoHub.Tests project file for consistency.
- Added unit tests for FileValidationHelper and PresenceTracker with improved assertions.
- Updated ValidationConstantsTests to ensure regex validations are correct.
- Cleaned up solution file formatting for better readability.

docs/api/index.md

@@ -1,17 +1,17 @@
-# API Reference
-
-Browse the generated API documentation for each EchoHub project.
-
-## Projects
-
-### Client
-
-Terminal.Gui v2 TUI application -- UI components, services, themes, and configuration.
-
-### Core
-
-Shared library -- DTOs, models, constants, and the SignalR client contract.
-
-### Server
-
-ASP.NET Core server -- controllers, hubs, authentication, and data access.
+# API Reference
+
+Browse the generated API documentation for each EchoHub project.
+
+## Projects
+
+### Client
+
+Terminal.Gui v2 TUI application -- UI components, services, themes, and configuration.
+
+### Core
+
+Shared library -- DTOs, models, constants, and the SignalR client contract.
+
+### Server
+
+ASP.NET Core server -- controllers, hubs, authentication, and data access.