feat(client): add ThemeSwitcher and relocate stories to .storybook/

- add lucide-react for Sun/Moon icons
- add useTheme hook persisting choice to localStorage with prefers-color-scheme fallback
- add ThemeSwitcher button component wired into SidePanel header
- add blocking inline script to index.html to prevent flash-of-wrong-theme
- move all *.stories.tsx from src/ into .storybook/stories/ and update imports
- update main.ts stories glob to .storybook/stories/**

package-lock.json

@@ -16,6 +16,7 @@
       "name": "liquio-qa-bot-client",
       "version": "0.0.1",
       "dependencies": {
+        "lucide-react": "^1.7.0",
         "react": "^19.1.0",
         "react-dom": "^19.1.0"
       },
@@ -9798,6 +9799,15 @@
         "node": "20 || >=22"
       }
     },
+    "node_modules/lucide-react": {
+      "version": "1.7.0",
+      "resolved": "https://registry.npmjs.org/lucide-react/-/lucide-react-1.7.0.tgz",
+      "integrity": "sha512-yI7BeItCLZJTXikmK4KNUGCKoGzSvbKlfCvw44bU4fXAL6v3gYS4uHD1jzsLkfwODYwI6Drw5Tu9Z5ulDe0TSg==",
+      "license": "ISC",
+      "peerDependencies": {
+        "react": "^16.5.1 || ^17.0.0 || ^18.0.0 || ^19.0.0"
+      }
+    },
     "node_modules/luxon": {
       "version": "3.7.2",
       "resolved": "https://registry.npmjs.org/luxon/-/luxon-3.7.2.tgz",