[FEATURE] Settings to set tokens for message history used

[dartpain]

This PR consists of 2 parts:

1. Frontend: Create UI in settings general menu to allow users to explicitly set amount of last characters used in current conversation to set how many will be used to process a new answer. Basically a little input field. Add it to the API keys dropdown too.
2. Backend: add parameters to /api/answer and /stream to include those limits for history of messages. Also add it to the /create api key endpoint.

Acceptance Criteria

• Scenario: User can set token length for message history in settings

  • Given the user is in the settings general menu
  • When the user inputs a value for the token length
  • Then the token length is saved and used for processing new answers

• Scenario: Backend API endpoints accept token length parameters

  • Given the user is using the API endpoints for answering and streaming messages
  • When the user includes the token length parameter in the request
  • Then the backend processes the request with the specified token length

• Scenario: Token length is applied to API key creation

  • Given the user is creating a new API key
  • When the user inputs the desired token length
  • Then the API key is generated with the specified token length for message history processing

[adi790uu]

@dartpain can you assign me this issue