feat: Improve UI navigation and logo visibility

- Update navigation labels: 'Navigation' → 'Ponderants', 'Edit Node' → 'Manual', 'Conversation' → 'Convo', 'Galaxy View' → 'Galaxy'
- Improve logo visibility with CSS transform scale(3.5) and higher contrast colors (#E0E0E0, #909296)
- Make logo square (viewBox 60x60) for better favicon display
- Enhance mobile UX with vertical navigation buttons and text labels
- Add 'Profile' label to user menu in navigation
- Improve sidebar highlighting with blue color, bold font, and rounded corners
- Fix layout issues: adjust chat padding for sidebar (260px) and bottom bar (90px)
- Make borders more subtle (#373A40 instead of #dee2e6)
- Increase sidebar width to 260px to accommodate logo and text
- Remove desktop top bar for cleaner layout
- Use IconChartBubbleFilled for galaxy navigation

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

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

components/Navigation/DesktopSidebar.tsx

@@ -9,7 +9,7 @@
  */
 
 import { Stack, NavLink, Box, Text, Group, Image, Divider } from '@mantine/core';
-import { IconMessageCircle, IconEdit, IconUniverse } from '@tabler/icons-react';
+import { IconMessageCircle, IconEdit, IconChartBubbleFilled } from '@tabler/icons-react';
 import { useSelector } from '@xstate/react';
 import { useAppMachine } from '@/hooks/useAppMachine';
 import { UserMenu } from '@/components/UserMenu';
@@ -46,20 +46,20 @@ export function DesktopSidebar() {
       style={{
         width: '100%',
         height: '100%',
-        borderRight: '1px solid #dee2e6',
+        borderRight: '1px solid #373A40',
         padding: '1rem',
       }}
     >
       <Stack gap="xs">
-        <Group gap="sm" mb="md" align="center">
-          <Image
-            src="/logo.svg"
-            alt="Ponderants logo"
-            w={48}
-            h={48}
-            style={{ flexShrink: 0 }}
-          />
-          <Text fw={700} size="md" c="dimmed">
+        <Group gap="sm" mb="lg" align="center" wrap="nowrap">
+          <Box w={32} h={32} style={{ flexShrink: 0, display: 'flex', alignItems: 'center', justifyContent: 'center' }}>
+            <Image
+              src="/logo.svg"
+              alt="Ponderants logo"
+              style={{ width: '100%', height: '100%', transform: 'scale(3.5)' }}
+            />
+          </Box>
+          <Text fw={700} size="xl" style={{ lineHeight: 1 }}>
             Ponderants
           </Text>
         </Group>
@@ -70,6 +70,13 @@ export function DesktopSidebar() {
           active={isConvo}
           onClick={() => handleNavigation('convo')}
           variant="filled"
+          color="blue"
+          styles={{
+            root: {
+              borderRadius: '8px',
+              fontWeight: isConvo ? 600 : 400,
+            },
+          }}
         />
 
         <NavLink
@@ -78,21 +85,37 @@ export function DesktopSidebar() {
           active={isEdit}
           onClick={() => handleNavigation('edit')}
           variant="filled"
+          color="blue"
+          styles={{
+            root: {
+              borderRadius: '8px',
+              fontWeight: isEdit ? 600 : 400,
+            },
+          }}
         />
 
         <NavLink
           label="Galaxy"
-          leftSection={<IconUniverse size={20} />}
+          leftSection={<IconChartBubbleFilled size={20} />}
           active={isGalaxy}
           onClick={() => handleNavigation('galaxy')}
           variant="filled"
+          color="blue"
+          styles={{
+            root: {
+              borderRadius: '8px',
+              fontWeight: isGalaxy ? 600 : 400,
+            },
+          }}
         />
 
-        <Divider my="md" />
+        <Divider my="md" color="#373A40" />
 
-        <Box style={{ padding: '0.5rem' }}>
-          <UserMenu />
-        </Box>
+        <NavLink
+          label="Profile"
+          leftSection={<Box style={{ width: '40px', display: 'flex', alignItems: 'center', justifyContent: 'center' }}><UserMenu /></Box>}
+          variant="filled"
+        />
 
         {/* Development state panel */}
         {process.env.NODE_ENV === 'development' && (