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/upload_content.html

@@ -0,0 +1,25 @@
+{% extends "base.html" %}
+
+{% block title %}Upload Content - DigiServer v2{% endblock %}
+
+{% block content %}
+<h1>Upload Content</h1>
+<div class="card">
+    <form method="POST" enctype="multipart/form-data">
+        <div style="margin-bottom: 1rem;">
+            <label>File</label>
+            <input type="file" name="file" required style="width: 100%; padding: 0.5rem;">
+        </div>
+        <div style="margin-bottom: 1rem;">
+            <label>Duration (seconds, for images)</label>
+            <input type="number" name="duration" value="10" min="1" style="width: 100%; padding: 0.5rem;">
+        </div>
+        <div style="margin-bottom: 1rem;">
+            <label>Description (optional)</label>
+            <textarea name="description" rows="3" style="width: 100%; padding: 0.5rem;"></textarea>
+        </div>
+        <button type="submit" class="btn btn-success">Upload</button>
+        <a href="{{ url_for('content.content_list') }}" class="btn">Cancel</a>
+    </form>
+</div>
+{% endblock %}