feat: Improve UI layout and navigation

- Increase logo size (48x48 desktop, 56x56 mobile) for better visibility
- Add logo as favicon
- Add logo to mobile header
- Move user menu to navigation bars (sidebar on desktop, bottom bar on mobile)
- Fix desktop chat layout - container structure prevents voice controls cutoff
- Fix mobile bottom bar - use icon-only ActionIcons instead of truncated text buttons
- Hide Create Node/New Conversation buttons on mobile to save header space
- Make fixed header and voice controls work properly with containers

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

AGENTS.md

@@ -11,6 +11,12 @@ EOF
 )"
 ```
 
+**Test Credentials**: For testing and development, use the test Bluesky account credentials stored in the .env file:
+- Handle: TEST_BLUESKY_HANDLE (aprongecko.bsky.social)
+- Password: TEST_BLUESKY_PASSWORD (Candles1)
+
+These credentials should be used for all automated testing (Magnitude, Playwright) and manual testing when needed. Do not attempt to authenticate without using these credentials.
+
 You are an expert-level, full-stack AI coding agent. Your task is to implement
 the "Ponderants" application. Product Vision: Ponderants is an AI-powered
 thought partner that interviews a user to capture, structure, and visualize