♻️ refactor(web): migrate React modules from .js to .jsx and align entrypoint

- Rename React components/pages/utilities that contain JSX to `.jsx` across `web/src`
- Update import paths and re-exports to match new `.jsx` extensions
- Fix Vite entry by switching `web/index.html` from `/src/index.js` to `/src/index.jsx`
- Verified remaining `.js` files are plain JS (hooks/helpers/constants) and do not require JSX
- No runtime behavior changes; extension and reference alignment only

Context: Resolves the Vite pre-transform error caused by the stale `/src/index.js` entry after migrating to `.jsx`.

web/src/context/Theme/index.jsx

@@ -0,0 +1,55 @@
+/*
+Copyright (C) 2025 QuantumNous
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Affero General Public License as
+published by the Free Software Foundation, either version 3 of the
+License, or (at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU Affero General Public License for more details.
+
+You should have received a copy of the GNU Affero General Public License
+along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+For commercial licensing, please contact support@quantumnous.com
+*/
+
+import { createContext, useCallback, useContext, useState } from 'react';
+
+const ThemeContext = createContext(null);
+export const useTheme = () => useContext(ThemeContext);
+
+const SetThemeContext = createContext(null);
+export const useSetTheme = () => useContext(SetThemeContext);
+
+export const ThemeProvider = ({ children }) => {
+  const [theme, _setTheme] = useState(() => {
+    try {
+      return localStorage.getItem('theme-mode') || null;
+    } catch {
+      return null;
+    }
+  });
+
+  const setTheme = useCallback((input) => {
+    _setTheme(input ? 'dark' : 'light');
+
+    const body = document.body;
+    if (!input) {
+      body.removeAttribute('theme-mode');
+      localStorage.setItem('theme-mode', 'light');
+    } else {
+      body.setAttribute('theme-mode', 'dark');
+      localStorage.setItem('theme-mode', 'dark');
+    }
+  }, []);
+
+  return (
+    <SetThemeContext.Provider value={setTheme}>
+      <ThemeContext.Provider value={theme}>{children}</ThemeContext.Provider>
+    </SetThemeContext.Provider>
+  );
+};