docs: Add dark/light theme screenshots and remove unused images

Add new screenshots for dashboard, chatbot, agent analytics, and
conversation flow builder in both dark and light themes. Update
README and docs pages to reference the new images. Remove 5 unused
images that were replaced.

Author: shridarpatil

README.md

@@ -4,7 +4,7 @@
 
 Modern, open-source WhatsApp Business Platform. Single binary app.
 
-![Dashboard](docs/public/images/01-dashboard.png)
+![Dashboard](docs/public/images/dashboard-dark.png)
 
 ## Features
 
@@ -38,8 +38,13 @@ Modern, open-source WhatsApp Business Platform. Single binary app.
 <details>
 <summary>View more screenshots</summary>
 
-![Chatbot Settings](docs/public/images/02-chatbot-settings.png)
-![Conversation Flow Builder](docs/public/images/08-conversation-flow-builder.png)
+![Dashboard Light](docs/public/images/dashboard-light.png)
+![Chatbot Dark](docs/public/images/chatbot-dark.png)
+![Chatbot Light](docs/public/images/chatbot-light.png)
+![Agent Analytics Dark](docs/public/images/agent-analytics-dark.png)
+![Agent Analytics Light](docs/public/images/agent-analytics-light.png)
+![Conversation Flow Builder Dark](docs/public/images/conversation-flow-dark.png)
+![Conversation Flow Builder Light](docs/public/images/conversation-flow-light.png)
 ![Templates](docs/public/images/11-templates.png)
 ![Campaigns](docs/public/images/13-campaigns.png)