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>

Gemfile.lock

@@ -625,6 +625,25 @@ GEM
       faraday (>= 1.0, < 3)
       multi_json (>= 1.0)
     openssl (3.2.0)
+    opentelemetry-api (1.7.0)
+    opentelemetry-common (0.23.0)
+      opentelemetry-api (~> 1.0)
+    opentelemetry-exporter-otlp (0.31.1)
+      google-protobuf (>= 3.18)
+      googleapis-common-protos-types (~> 1.3)
+      opentelemetry-api (~> 1.1)
+      opentelemetry-common (~> 0.20)
+      opentelemetry-sdk (~> 1.10)
+      opentelemetry-semantic_conventions
+    opentelemetry-registry (0.4.0)
+      opentelemetry-api (~> 1.1)
+    opentelemetry-sdk (1.10.0)
+      opentelemetry-api (~> 1.1)
+      opentelemetry-common (~> 0.20)
+      opentelemetry-registry (~> 0.2)
+      opentelemetry-semantic_conventions
+    opentelemetry-semantic_conventions (1.36.0)
+      opentelemetry-api (~> 1.0)
     orm_adapter (0.5.0)
     os (1.1.4)
     ostruct (0.6.1)
@@ -1073,6 +1092,8 @@ DEPENDENCIES
   omniauth-rails_csrf_protection (~> 1.0, >= 1.0.2)
   omniauth-saml
   opensearch-ruby
+  opentelemetry-exporter-otlp
+  opentelemetry-sdk
   pg
   pg_search
   pgvector