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>

tests/helpers/README.md

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+# Playwright Test Helpers
+
+This directory contains reusable helper functions for both Magnitude tests and Playwright MCP testing.
+
+## Usage
+
+### In Magnitude Tests
+
+```typescript
+import { test } from 'magnitude-test';
+import {
+  navigateToApp,
+  loginWithBluesky,
+  startConversation,
+  createNodeDraft,
+  publishNode,
+  completeNodePublishFlow,
+} from '../helpers/playwright-helpers';
+
+test('User can publish a node', async (agent) => {
+  const page = agent.page; // Get Playwright page from Magnitude agent
+
+  await completeNodePublishFlow(page, 'My test conversation');
+
+  await agent.check('Node published successfully');
+});
+```
+
+### In Playwright MCP
+
+Use the helper functions directly with the Playwright MCP page instance:
+
+```typescript
+import { loginWithBluesky, startConversation } from './tests/helpers/playwright-helpers';
+
+// In your MCP session
+await loginWithBluesky(page);
+await startConversation(page, 'Hello AI');
+```
+
+## Available Helpers
+
+### Authentication
+- `loginWithBluesky(page, credentials?)` - Complete OAuth login flow
+- `logout(page)` - Logout from application
+- `isLoggedIn(page)` - Check if user is authenticated
+
+### Navigation
+- `navigateToApp(page, baseUrl?)` - Go to app home page
+
+### Conversation
+- `startConversation(page, message)` - Send first message in chat
+- `waitForAIResponse(page, timeout?)` - Wait for AI to finish responding
+
+### Node Publishing
+- `createNodeDraft(page)` - Click "Create Node" button
+- `editNodeDraft(page, title?, content?)` - Modify draft before publishing
+- `publishNode(page)` - Click "Publish" and wait for success
+- `completeNodePublishFlow(page, message?, credentials?)` - Full end-to-end flow
+
+## Environment Variables
+
+Set these in your `.env.test` file:
+
+```env
+TEST_BLUESKY_USERNAME=your-test-user.bsky.social
+TEST_BLUESKY_PASSWORD=your-test-password
+```
+
+If not set, helpers will use default values (which will fail for real OAuth).
+
+## Design Principles
+
+1. **Reusability** - Each helper is atomic and can be composed
+2. **Reliability** - Helpers wait for network and UI state before proceeding
+3. **Flexibility** - Optional parameters allow customization
+4. **Error Handling** - Helpers throw clear errors when expectations aren't met