feat: Add DatabaseManager and LinkPlayer components, implement authentication and linking logic

- Created DatabaseManager component for managing database access via phpMyAdmin.
- Developed LinkPlayer component to link Discord accounts with game characters, including user authentication and error handling.
- Added mock data files for players, organizations, and projects to handle backend unavailability.
- Implemented AuthService for managing user authentication and session checks.
- Created DatabaseService to fetch and manage player, organization, and project data with fallback to mock data.
- Added HTML page for handling authentication unavailability.
- Developed a test script for validating Docker setup and required files.

constants.ts

@@ -65,7 +65,7 @@ Spezialisiert auf automatisierte Logistik. Gerüchten zufolge hat er eine Maschi
   },
   {
     uuid: 'b3b84518-03a2-4b48-8551-448c3f7a7d77',
-    username: 'ceratic',
+    username: 'ceratic_test',
     isOnline: true,
     tags: ['#Bürger', '#Händler'],
     stats: {