fix: improve theming and settings visibility

- Fix namespace detail panel to follow system dark/light theme
- Use proper CSS custom properties for background and text colors
- Fix plugin settings registration (remove deprecated third parameter)
- Ensure close button and headers respect theme colors
- Version bump to 0.2.5

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

src/components/NamespacesListView.tsx

@@ -103,7 +103,7 @@ function NamespaceDetailPanel({ namespace, onClose }: NamespaceDetailPanelProps)
         top: 0,
         bottom: 0,
         width: '1000px',
-        backgroundColor: 'var(--background-paper, #fff)',
+        backgroundColor: 'var(--mui-palette-background-paper, var(--background-paper, #fff))',
         boxShadow: '-2px 0 8px rgba(0,0,0,0.15)',
         overflowY: 'auto',
         zIndex: 1200,
@@ -118,7 +118,7 @@ function NamespaceDetailPanel({ namespace, onClose }: NamespaceDetailPanelProps)
           alignItems: 'center',
         }}
       >
-        <h2 style={{ margin: 0 }}>Polaris — {namespace}</h2>
+        <h2 style={{ margin: 0, color: 'var(--mui-palette-text-primary, var(--text-primary, #000))' }}>Polaris — {namespace}</h2>
         <button
           onClick={onClose}
           style={{
@@ -127,6 +127,7 @@ function NamespaceDetailPanel({ namespace, onClose }: NamespaceDetailPanelProps)
             fontSize: '24px',
             cursor: 'pointer',
             padding: '0 8px',
+            color: 'var(--mui-palette-text-primary, var(--text-primary, #000))',
           }}
           aria-label="Close panel"
         >