Add admin features, user profile management, and generation capabilities

- Implemented admin dashboard with user management features including role assignment and deletion.
- Added user profile page for updating email and password.
- Created separate routes and templates for text, image, and video generation with appropriate forms.
- Enhanced navigation with dropdown for generation options and loading overlay for better user experience.
- Introduced comprehensive error handling and user feedback through alerts.
- Updated styles for improved UI consistency and responsiveness.

Co-authored-by: Copilot <copilot@github.com>

frontend/app/static/app.js

@@ -0,0 +1,36 @@
+document.addEventListener('DOMContentLoaded', () => {
+  // ── Loading overlay ────────────────────────────────────
+  const overlay = document.getElementById('loading-overlay');
+
+  document.querySelectorAll('form').forEach((form) => {
+    form.addEventListener('submit', () => {
+      if (overlay) overlay.classList.add('active');
+    });
+  });
+
+  // ── Hamburger menu ─────────────────────────────────────
+  const hamburger = document.querySelector('.hamburger');
+  const navLinks = document.querySelector('.nav-links');
+
+  if (hamburger && navLinks) {
+    hamburger.addEventListener('click', () => {
+      navLinks.classList.toggle('open');
+    });
+  }
+
+  // ── Generate dropdown tabs ─────────────────────────────
+  document.querySelectorAll('.tab-btn').forEach((btn) => {
+    btn.addEventListener('click', () => {
+      const target = btn.dataset.tab;
+      const container = btn.closest('.tabs-container');
+      if (!container) return;
+
+      container.querySelectorAll('.tab-btn').forEach((b) => b.classList.remove('active'));
+      container.querySelectorAll('.tab-panel').forEach((p) => p.classList.remove('active'));
+
+      btn.classList.add('active');
+      const panel = container.querySelector(`#tab-${target}`);
+      if (panel) panel.classList.add('active');
+    });
+  });
+});