Add comprehensive documentation for DMARQ, including user guides, deployment instructions, and feature descriptions

- Created main documentation index and user guide with sections on getting started, dashboard overview, managing domains, and reports.
- Added detailed deployment guide for Docker and manual installation.
- Included user-friendly explanations of DMARC, its benefits, and how to manage domains and reports.
- Implemented visual assets for dashboard, domains, IMAP, and reports.
- Established requirements for documentation build using MkDocs and Material theme.
- Integrated navigation structure for easy access to all documentation sections.

docs/index.md

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+# DMARQ Documentation
+
+Welcome to the official documentation for DMARQ - a comprehensive DMARC reporting and analysis tool.
+
+DMARQ helps organizations monitor their email authentication status, analyze DMARC reports, and improve email deliverability and security.
+
+## What is DMARQ?
+
+DMARQ is a full-stack DMARC monitoring platform designed to help organizations track and improve their email authentication. It processes DMARC reports (aggregate and forensic) and presents compliance insights via a user-friendly dashboard.
+
+## Key Features
+
+- **DMARC Report Processing**: Automatically collect and parse DMARC aggregate and forensic reports
+- **Interactive Dashboard**: Visualize compliance rates and authentication trends
+- **DNS Health Checks**: Verify your email authentication records (SPF, DKIM, DMARC)
+- **IMAP Integration**: Automatically fetch reports from your email inbox
+- **Alerting**: Get notified about important authentication issues
+- **Easy Setup**: Web-based configuration wizard for quick onboarding
+
+## Getting Started
+
+To get started with DMARQ, please see the [Getting Started](user_guide/getting_started.md) guide.
+
+For installation instructions, check the [Docker Setup](deployment/docker.md) or [Manual Installation](deployment/manual.md) guides.