Suggestion: Use "anthropic-dangerous-direct-browser-access" for Anthropic to resolve cors issues

[kappuchino]

Is your feature request related to a problem? Please describe.
Currently API Calls are routed through the flask backend. Anthropic has kind of silently introduced the "anthropic-dangerous-direct-browser-access" header to allow cors calls from everywhere

Describe the solution you'd like
Harmonize the calls to providers. For anthropic it could now be like

// Make a REST call to Anthropic
  // Repeat call n times, waiting for each response to come in:
  const responses: Array<Dict> = [];
  while (responses.length < n) {
    // Abort if canceled
    if (should_cancel && should_cancel()) throw new UserForcedPrematureExit();

    // Direct API call to Anthropic (harmonized with other providers)
    const url = `https://api.anthropic.com/v1/${
      use_messages_api ? "messages" : "complete"
    }`;

    const headers = {
      "x-api-key": ANTHROPIC_API_KEY,
      "anthropic-version": "2023-06-01",
      "content-type": "application/json",
      "anthropic-dangerous-direct-browser-access": "true", // Enable direct browser access
    };

[...]

Additional context
See this Issue for details.