Enhance Swagger UI with modern styling and improved documentation

[Copilot]

Issue requested UI improvements for the API. Enhanced Swagger UI with custom styling, better organization, and comprehensive endpoint documentation.

Changes

Custom Styling (wwwroot/css/swagger-custom.css)

• Gradient background (purple/blue), modern card layout with shadows and animations
• Color-coded HTTP methods (GET=green, POST=blue, PUT=orange, DELETE=red)
• Enhanced typography, hover effects, and responsive design

Swagger Configuration (Program.cs)

app.UseStaticFiles();
app.UseSwaggerUI(options =>
{
    options.InjectStylesheet("/css/swagger-custom.css");
    options.DocumentTitle = "Tailwind Traders Mail API";
    options.EnableDeepLinking();
    options.EnableFilter();
    options.DisplayRequestDuration();
});

Enhanced API Documentation

• Added emoji prefixes to endpoint summaries for visual scanning (📧 📤 🔍 🏷️ 🤖)
• Organized endpoints into logical tags: Public, Admin - Broadcasts, Admin - Contacts, Admin - Bulk Operations, Admin - AI Assistant
• Updated OpenAPI info with features list and getting started guide
• Expanded endpoint descriptions with context and use cases

Routes Updated

All route files enhanced with:

.WithOpenApi(op => {
  op.Summary = "📤 Queue Email Broadcast";
  op.Description = "Creates and queues a new broadcast email campaign from markdown content. Messages will be sent to all opted-in contacts.";
  return op;
}).WithTags("Admin - Broadcasts");

Visual Changes

Before: Default Swagger UI with minimal styling
After: Professional, branded interface with improved navigation

Security

CodeQL: 0 vulnerabilities

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[Bug]: Make the UI better</issue_title>
<issue_description>### Contact Details

No response

What happened?

A bug happened!

Version

1.0.2 (Default)

What browsers are you seeing the problem on?

No response

Relevant log output

Code of Conduct

• I agree to follow this project's Code of Conduct</issue_description>

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

• Fixes [Bug]: Make the UI better #63

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