Add Gemini streaming support to brochure generator

[SAMK-online]

Add Gemini Streaming Support to Brochure Generator

This PR adds support for using Google's Gemini model in the brochure generator, alongside the existing GPT and Claude options.

Changes

• Added stream_gemini function to handle Gemini API streaming responses
• Updated stream_brochure to support Gemini model option
• Added Gemini to model dropdown in UI
• Maintains consistent streaming pattern with GPT and Claude implementations

Implementation Details

• Uses Gemini's streaming API with the same pattern as GPT and Claude
• Handles streaming chunks consistently with other models
• Preserves markdown formatting in responses
• Maintains same error handling pattern as other models

Testing

The implementation has been tested with:

• Basic company website URLs
• Streaming functionality works as expected
• UI updates in real-time as responses are generated

Requirements

• Requires Google API key to be configured (same as existing setup)
• Uses gemini-2.5-flash model for optimal performance
• No additional dependencies required beyond existing ones

Notes

• Follows the same streaming pattern as existing models for consistency
• Uses the OpenAI-compatible endpoint for better integration
• Maintains the same error handling patterns

[ed-donner]

Hey - this PR seems to be changing an existing file in the repo - was that intentional? Ed