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.

Dockerfile.frontend

@@ -0,0 +1,33 @@
+# Frontend Dockerfile
+FROM node:20-alpine AS builder
+
+# Set working directory
+WORKDIR /app
+
+# Copy package files
+COPY package.json .
+
+# Install dependencies
+RUN npm install
+
+# Copy source files
+COPY . .
+COPY public /app/public
+
+# Build the application
+RUN npm run build
+
+# Production stage
+FROM nginx:alpine
+
+# Copy built files from builder
+COPY --from=builder /app/dist /usr/share/nginx/html
+
+# Copy custom nginx configuration
+COPY nginx.conf /etc/nginx/conf.d/default.conf
+
+# Expose port
+EXPOSE 80
+
+# Start nginx
+CMD ["nginx", "-g", "daemon off;"]