More control over the embedded interview flow

• Embedded conversation flow controls: Skip the welcome screen and start directly in voice or text, and immediately redirect on completion when a return URL is provided.
• Embed SDK migration: Embed now ships via published @perspective-ai/sdk and @perspective-ai/sdk-react packages with global CDN delivery for faster loads.
• UI theming: Custom theme support for chat input buttons and user message bubbles.

Simplified connection messages, tooltips, and prompts in the voice input for clarity.

Conversation header now always shows a logo, defaulting to the Perspective logo when no custom logo is set.