feat: Add support for Langfuse LLM Tracing via OTEL (#12905)

This PR adds LLM instrumentation on langfuse for ai-editor feature

## Type of change
New feature (non-breaking change which adds functionality)

Needs langfuse account and env vars to be set

## How Has This Been Tested?

I configured personal langfuse credentials and instrumented the app,
traces can be seen in langfuse.
each conversation is one session. 
<img width="1683" height="714" alt="image"
src="https://github.com/user-attachments/assets/3fcba1c9-63cf-44b9-a355-fd6608691559"
/>
<img width="1446" height="172" alt="image"
src="https://github.com/user-attachments/assets/dfa6e98f-4741-4e04-9a9e-078d1f01e97b"
/>


## Checklist:

- [x ] My code follows the style guidelines of this project
- [ x] I have performed a self-review of my code
- [ x] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [ x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

---------

Co-authored-by: aakashb95 <aakash@chatwoot.com>
Co-authored-by: Vishnu Narayanan <iamwishnu@gmail.com>
Co-authored-by: Pranav <pranav@chatwoot.com>

config/installation_config.yml

@@ -199,7 +199,6 @@
   description: 'The limits for the Captain AI service for different plans'
   value:
   type: code
-
 # End of Captain Config
 
 # ------- Chatwoot Internal Config for Cloud ----#
@@ -476,3 +475,28 @@
   locked: false
   description: 'Token expiry in days'
 ## ------ End of Customizations for Customers ------ ##
+
+## ----- LLM Observability ---- ##
+- name: OTEL_PROVIDER
+  display_title: 'OpenTelemetry Provider'
+  description: 'LLM observability provider (langfuse, langsmith, etc.)'
+  value: ''
+  locked: false
+- name: LANGFUSE_PUBLIC_KEY
+  display_title: 'Langfuse Public Key'
+  description: 'Public key for Langfuse authentication'
+  value: ''
+  locked: false
+  type: secret
+- name: LANGFUSE_SECRET_KEY
+  display_title: 'Langfuse Secret Key'
+  description: 'Secret key for Langfuse authentication'
+  value: ''
+  locked: false
+  type: secret
+- name: LANGFUSE_BASE_URL
+  display_title: 'Langfuse Base URL'
+  description: 'Langfuse endpoint (US: https://us.cloud.langfuse.com, EU: https://cloud.langfuse.com)'
+  value: 'https://us.cloud.langfuse.com'
+  locked: false
+## ---- End of LLM Observability ---- ##