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/toc.yml

@@ -1,18 +1,18 @@
-- name: Client
-  items:
-    - name: API Reference
-      href: ../_api_meta/client/toc.yml
-    - name: Articles
-      href: client-articles/
-- name: Core
-  items:
-    - name: API Reference
-      href: ../_api_meta/core/toc.yml
-    - name: Articles
-      href: core-articles/
-- name: Server
-  items:
-    - name: API Reference
-      href: ../_api_meta/server/toc.yml
-    - name: Articles
-      href: server-articles/
+- name: Client
+  items:
+    - name: API Reference
+      href: ../_api_meta/client/toc.yml
+    - name: Articles
+      href: client-articles/
+- name: Core
+  items:
+    - name: API Reference
+      href: ../_api_meta/core/toc.yml
+    - name: Articles
+      href: core-articles/
+- name: Server
+  items:
+    - name: API Reference
+      href: ../_api_meta/server/toc.yml
+    - name: Articles
+      href: server-articles/