Implement support for generic OpenAI api (#213)

* Implement support for generic OpenAI api

- Implements support to route requests to any openAI capable provider ( Deepsek, Qwen, VLLM, LM Studio, Ollama ).
- Keeps support for pure OpenAI and uses the new better responses api
- Uses the /chat/completions api for the generic providers
- If uri_base is not set, uses default implementation.

* Fix json handling and indentation

* Fix linter error indent

* Fix tests to set env vars

* Fix updating settings

* Change to prefix checking for OAI models

* FIX check model if custom uri is set

* Change chat to sync calls

Some local models don't support streaming. Revert to sync calls for generic OAI api

* Fix tests

* Fix tests

* Fix for gpt5 message extraction

- Finds the message output by filtering for "type" == "message" instead of assuming it's at index 0
- Safely extracts the text using safe navigation operators (&.)
- Raises a clear error if no message content is found
- Parses the JSON as before

* Add more langfuse logging

- Add Langfuse to auto categorizer and merchant detector
- Fix monitoring on streaming chat responses
- Add Langfuse traces also for model errors now

* Update app/models/provider/openai.rb

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>
Signed-off-by: soky srm <sokysrm@gmail.com>

* handle nil function results explicitly

* Exposing some config vars.

* Linter and nitpick comments

* Drop back to `gpt-4.1` as default for now

* Linter

* Fix for strict tool schema in Gemini

- This fixes tool calling in Gemini OpenAI api
- Fix for getTransactions function, page size is not used.

---------

Signed-off-by: soky srm <sokysrm@gmail.com>
Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>
Co-authored-by: Juan José Mata <juanjo.mata@gmail.com>

app/views/messages/_chat_form.html.erb

@@ -8,7 +8,7 @@
                 data: { chat_target: "form" } do |f| %>
 
     <%# In the future, this will be a dropdown with different AI models %>
-    <%= f.hidden_field :ai_model, value: "gpt-4.1" %>
+    <%= f.hidden_field :ai_model, value: default_ai_model %>
 
     <%= f.text_area :content, placeholder: "Ask anything ...", value: message_hint,
                   class: "w-full border-0 focus:ring-0 text-sm resize-none px-1 bg-transparent",