Refactor settings system and improve context initialization

Backend:
- Add type validation and coercion for settings API
- Implement SettingStorage and SettingType in registry
- Improve CRUD operations for settings

Frontend:
- Refactor Theme, Language, Sidebar, ViewMode contexts
- Simplify admin components (GeneralTab, SettingsTab, UsersTab)
- Add new settings endpoints to API client
- Improve App initialization flow

Infrastructure:
- Update Dockerfile and docker-compose.yml
- Add .dockerignore
- Update Makefile and README

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/pages/Feature2.tsx

@@ -0,0 +1,36 @@
+import { useTranslation } from '../contexts/LanguageContext';
+import { useSidebar } from '../contexts/SidebarContext';
+import '../styles/AdminPanel.css';
+
+export default function Feature2() {
+  const { t } = useTranslation();
+  const { toggleMobileMenu } = useSidebar();
+
+  return (
+    <main className="main-content">
+      <div className="page-tabs-container">
+        <div className="page-tabs-slider">
+          <button className="mobile-menu-btn" onClick={toggleMobileMenu} aria-label={t.theme.toggleMenu}>
+            <span className="material-symbols-outlined">menu</span>
+          </button>
+          <div className="page-title-section">
+            <span className="material-symbols-outlined">download</span>
+            <span className="page-title-text">{t.features.feature2}</span>
+          </div>
+        </div>
+      </div>
+
+      <div className="page-content">
+        <div className="tab-content-placeholder">
+          <div className="placeholder-icon">
+            <span className="material-symbols-outlined">download</span>
+          </div>
+
+          <h3>{t.features.feature2}</h3>
+          <p>{t.features.comingSoon}</p>
+        </div>
+      </div>
+    </main>
+  );
+}
+