feat: Implement UI for Agent Bots in settings and remove CSML support (#11276)

- Add agent bots management UI in settings with avatar upload
- Enable agent bot configuration for all inbox types
- Implement proper CRUD operations with webhook URL support
- Fix agent bots menu item visibility in settings sidebar
- Remove all CSML-related code and features
- Add migration to convert existing CSML bots to webhook bots
- Simplify agent bot model and services to focus on webhook bots
- Improve UI to differentiate between system bots and account bots

## Video 





https://github.com/user-attachments/assets/3f4edbb7-b758-468c-8dd6-a9537b983f7d

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Co-authored-by: iamsivin <iamsivin@gmail.com>
Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>
Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>
Co-authored-by: Pranav <pranav@chatwoot.com>

app/views/api/v1/models/_agent_bot.json.jbuilder

@@ -1,8 +1,10 @@
 json.id resource.id
 json.name resource.name
 json.description resource.description
-json.outgoing_url resource.outgoing_url
+json.thumbnail resource.avatar_url
+json.outgoing_url resource.outgoing_url unless resource.system_bot?
 json.bot_type resource.bot_type
 json.bot_config resource.bot_config
 json.account_id resource.account_id
 json.access_token resource.access_token if resource.access_token.present?
+json.system_bot resource.system_bot?