Enforce uppercase README.md and TODO.md filenames

- Renamed all Readme.md → README.md
- Renamed all Todo.md → TODO.md
- Added integration test (tests/integration/test_filename_conventions.py) to automatically check naming convention.

Background:
Consistency in file naming (uppercase README.md and TODO.md) avoids issues with case-sensitive filesystems and ensures desktop cards (e.g. Pretix) are properly included.
Ref: https://chatgpt.com/share/68b1d135-c688-800f-9441-46a3cbfee175

docs/guides/user/README.md

@@ -0,0 +1,66 @@
+# User Guide
+
+Welcome to **Infinito.Nexus**! This guide is designed for **end-users** who want to use cloud services, email, and collaboration tools securely and efficiently. Whether you're an **enterprise user** or an **individual**, Infinito.Nexus provides a wide range of services tailored to your needs.
+
+## What Can Infinito.Nexus Do for You? 💡
+Infinito.Nexus enables you to securely and efficiently use a variety of **cloud-based applications**, including:
+
+### 📂 Cloud Storage & File Sharing
+- **Nextcloud** – Securely store, sync, and share files across devices.
+- **OnlyOffice** – Work on documents, spreadsheets, and presentations directly within Nextcloud.
+- **LibreOffice** – A powerful office suite alternative to Microsoft Office.
+
+### 💬 Secure Communication & Collaboration
+- **Matrix (Element)** – Encrypted messaging for teams and individuals.
+- **XMPP** – Secure instant messaging with various supported clients.
+- **Mailu** – A private, self-hosted email solution.
+- **Etherpad** – Real-time collaborative document editing.
+- **BigBlueButton** – Web conferencing with screen sharing and presentations.
+- **Jitsi** – Secure video conferencing without account requirements.
+
+### 🎵 Social Media & Content Sharing
+- **Mastodon** – Decentralized microblogging platform (alternative to Twitter/X).
+- **Pixelfed** – Decentralized image sharing (alternative to Instagram).
+- **Friendica** – Social network supporting federation with Mastodon and others.
+- **Peertube** – Decentralized video streaming platform (alternative to YouTube).
+- **Funkwhale** – Self-hosted music streaming for individuals and communities.
+
+### 🎮 Entertainment & Media
+- **Jellyfin** – Open-source media server for movies, TV, and music.
+- **Kodi** – Media center application with extensive plugin support.
+- **qBittorrent** – Open-source torrent client with secure remote access.
+
+### 🔒 Privacy & Security
+- **WireGuard** – Secure and fast VPN solution.
+- **Tor Browser** – Browse the web anonymously and bypass censorship.
+- **Bitwarden** – Open-source password manager for secure credential storage.
+- **2FA Authentication** – Securely log in to your services with Two-Factor Authentication.
+
+### 🔧 Developer & Productivity Tools
+- **Gitea** – Self-hosted Git repository management (alternative to GitHub/GitLab).
+- **Jenkins** – Automate software development pipelines.
+- **Discourse** – Community discussion forums for support and engagement.
+- **MediaWiki** – Create and manage knowledge bases and wikis.
+
+## 🏢 Enterprise Users
+### How to Get Started 🏁
+If your organization provides Infinito.Nexus services, follow these steps:
+- Your **administrator** will provide login credentials.
+- Access **cloud services** via a web browser or mobile apps.
+- For support, contact your **system administrator**.
+
+## 🏠 Private Users
+### How to Get Started 🏁
+If you're an **individual user**, you can sign up for Infinito.Nexus services:
+- **Register an account** at [infinito.nexus](https://infinito.nexus).
+- Choose the applications and services you need.
+- Follow the setup guide and start using Infinito.Nexus services immediately.
+
+## 📚 Learn More
+Discover more about Infinito.Nexus applications:
+- :doc:`roles/application_glosar`
+- :doc:`roles/application_categories`
+
+For further information, visit our **[Information Hub](https://hub.infinito.nexus)** for tutorials, FAQs, and community support.
+
+You can also register for updates and support from our community.