Add development testing environment

Templates (8 basic templates):
- base.html: Main layout with navigation, flash messages, responsive design
- login.html: User login form with remember me option
- register.html: User registration with validation
- dashboard.html: Main dashboard with statistics cards and recent activity
- players_list.html: Players list placeholder
- add_player.html: Add player form
- groups_list.html: Groups list placeholder
- create_group.html: Create group form
- content_list.html: Content list placeholder
- upload_content.html: File upload form
- admin.html: Admin panel with system overview

Development Setup:
- run_dev.sh: Automated development server setup script
  - Creates virtual environment
  - Installs dependencies
  - Initializes database
  - Creates default admin user (admin/admin123)
  - Runs Flask development server on port 5000

Static Files:
- static/uploads/ directory with .gitkeep
- Ready for media file uploads

Testing Features:
✅ Basic navigation and routing
✅ Authentication flow (login/register/logout)
✅ Dashboard with statistics
✅ Flash message system
✅ Responsive design with clean UI
✅ Placeholder templates for all routes

Ready for manual testing at http://localhost:5000

app/templates/groups_list.html

@@ -0,0 +1,11 @@
+{% extends "base.html" %}
+
+{% block title %}Groups - DigiServer v2{% endblock %}
+
+{% block content %}
+<h1>Groups</h1>
+<div class="card">
+    <p>Groups list view - Template in progress</p>
+    <a href="{{ url_for('groups.create_group') }}" class="btn btn-success">Create New Group</a>
+</div>
+{% endblock %}