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.

.env

@@ -0,0 +1,14 @@
+# Discord OAuth Configuration
+DISCORD_CLIENT_ID=1454649755513655491
+DISCORD_CLIENT_SECRET=TqGBxbyE3NBoJCp1riuu2eJe6Y_0zwtu
+
+# Session Security
+SESSION_SECRET=dhu2rb9gt82vrn9th2847t2nv45t8v29n4g5tu4gtib
+
+# Note: Replace the placeholder values above with your actual Discord application credentials
+# Get these from: https://discord.com/developers/applications
+
+DB_HOST=db
+DB_USER=obsidian_user
+DB_PASS=obsidian_pass
+DB_NAME=obsidian_db