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.

.editorconfig

@@ -0,0 +1,24 @@
+root = true
+
+[*]
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+charset = utf-8
+indent_style = space
+indent_size = 4
+
+[*.{cs,csx}]
+indent_size = 4
+
+[*.{json,yml,yaml}]
+indent_size = 2
+
+[*.{xml,csproj,props,targets,slnx}]
+indent_size = 2
+
+[*.md]
+trim_trailing_whitespace = false
+
+[Makefile]
+indent_style = tab