Add comprehensive Tailwind CSS development guidelines (German & English)

[Copilot]

Overview

This PR adds comprehensive development guidelines documenting the Tailwind CSS framework usage for the Trailmarks.io homepage, addressing issue #[issue-number] which requested documentation of the existing Tailwind CSS implementation.

What's New

Documentation Files Created

1. DEVELOPMENT.md (English, 8.9 KB)

   • Complete Tailwind CSS styling framework documentation
   • Custom components and utilities reference
   • Development workflow and commands
   • Coding standards and best practices
   • Testing and deployment procedures
   • Troubleshooting guide

2. DEVELOPMENT.de.md (German, 9.6 KB)

   • Full German translation of all development guidelines
   • Same comprehensive coverage for German-speaking developers

Enhanced README.md

• Streamlined Quick Start section
• Enhanced Design System section with Tailwind CSS emphasis
• Added prominent references to both language versions of guidelines
• Better organized brand colors with usage descriptions

Key Documentation Coverage

Tailwind CSS Framework

• Utility-First Approach: Clear guidelines on using Tailwind utility classes directly in HTML
• No Inline Styles Policy: Explicit prohibition of inline style="" attributes
• Custom Brand Colors: Documentation of all five brand colors (blue, green, orange, stone, earth)
• Typography System: Poppins for display text, Inter for body text

Custom Components Documented

.btn-primary       → Primary action buttons (blue background, white text)
.btn-secondary     → Secondary action buttons (white with blue border)
.section-padding   → Standard responsive section spacing

Development Standards

• HTML semantic requirements
• Tailwind class ordering conventions
• Responsive design patterns (mobile-first with sm/md/lg breakpoints)
• Common component patterns (containers, cards, gradients)
• Accessibility guidelines
• Internationalization handling (German/English)

Verification

• ✅ CSS builds successfully with npm run build-css-prod
• ✅ No inline styles found in codebase
• ✅ All styling uses Tailwind utility classes exclusively
• ✅ Documentation available in both German and English

Impact

• +802 lines of comprehensive documentation
• Bilingual support for international development team
• Clear standards for all future development
• Complete reference for Tailwind CSS framework usage

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Resolves: CSS Stylings basierend auf Tailwind CSS - Diese soll auch den Instructions bzw. den Entwicklungsrichtlinien hinzugefügt werden

Original prompt

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This section details on the original issue you should resolve

<issue_title>CSS Stylings basierend auf Tailwind CSS</issue_title>
<issue_description>Bitte setze das bestehende Styling und Layout mit dem Tailwind CSS Framework um.

Diese soll auch den Instructions bzw. den Entwicklungsrichtlinien hinzugefügt werden </issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #7

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