feat: add admin dark mode and SEO/robots.txt settings

Admin Dark Mode:
- Add AdminDarkModeContext with light/dark/system preference
- Update all admin components with Tailwind dark: classes
- Add dark mode toggle in admin header
- Persist preference in localStorage

SEO Settings:
- Add robots.txt configuration in Settings > SEO tab
- Block AI crawlers (GPTBot, ChatGPT-User, etc.) with toggle
- Custom robots.txt rules management
- Add RobotsMetaTags component for gallery pages
- Backend service for dynamic robots.txt generation
- Database migration for SEO settings storage

UI/UX Improvements:
- Consistent dark mode styling across all admin pages
- Update gallery components with themed CSS classes
- Fix input, card, and button styling for dark mode

backend/src/routes/adminSettings.js

@@ -733,6 +733,70 @@ router.put('/analytics', adminAuth, requirePermission('settings.edit'), async (r
   }
 });
 
+// Update SEO settings
+router.put('/seo', adminAuth, requirePermission('settings.edit'), async (req, res) => {
+  try {
+    const settings = req.body;
+
+    // Validate seo_blocked_ai_agents is an array of strings
+    if (settings.seo_blocked_ai_agents !== undefined) {
+      if (!Array.isArray(settings.seo_blocked_ai_agents) ||
+          !settings.seo_blocked_ai_agents.every(a => typeof a === 'string')) {
+        return res.status(400).json({ error: 'seo_blocked_ai_agents must be an array of strings' });
+      }
+    }
+
+    // Validate seo_custom_rules structure
+    if (settings.seo_custom_rules !== undefined) {
+      if (!Array.isArray(settings.seo_custom_rules)) {
+        return res.status(400).json({ error: 'seo_custom_rules must be an array' });
+      }
+      for (const rule of settings.seo_custom_rules) {
+        if (!rule.userAgent || typeof rule.userAgent !== 'string') {
+          return res.status(400).json({ error: 'Each custom rule must have a userAgent string' });
+        }
+        if (!Array.isArray(rule.disallow) || !rule.disallow.every(d => typeof d === 'string')) {
+          return res.status(400).json({ error: 'Each custom rule must have a disallow array of strings' });
+        }
+      }
+    }
+
+    // Update or insert each setting
+    for (const [key, value] of Object.entries(settings)) {
+      await db('app_settings')
+        .insert({
+          setting_key: key,
+          setting_value: JSON.stringify(value),
+          setting_type: 'seo',
+          updated_at: new Date()
+        })
+        .onConflict('setting_key')
+        .merge({
+          setting_value: JSON.stringify(value),
+          updated_at: new Date()
+        });
+    }
+
+    // Clear robots.txt cache
+    const { clearRobotsTxtCache } = require('../services/robotsTxtService');
+    clearRobotsTxtCache();
+
+    // Log activity
+    await db('activity_logs').insert({
+      activity_type: 'seo_settings_updated',
+      actor_type: 'admin',
+      actor_id: req.admin.id,
+      actor_name: req.admin.username,
+      metadata: JSON.stringify({ settings_count: Object.keys(settings).length })
+    });
+
+    res.json({ message: 'SEO settings updated successfully' });
+  } catch (error) {
+    console.error('SEO settings update error:', error);
+    res.status(500).json({ error: 'Failed to update SEO settings' });
+  }
+});
+
 // Get storage info
 router.get('/storage/info', adminAuth, requirePermission('settings.view'), async (req, res) => {
   try {

backend/src/routes/publicSettings.js

@@ -12,7 +12,8 @@ router.get('/', async (req, res) => {
         .where(function() {
           this.whereIn('setting_type', ['branding', 'theme', 'general', 'security', 'analytics', 'boolean'])
             .orWhere('setting_key', 'like', 'analytics_%')
-            .orWhere('setting_key', 'like', 'event_require_%');
+            .orWhere('setting_key', 'like', 'event_require_%')
+            .orWhereIn('setting_key', ['seo_meta_noindex', 'seo_meta_nofollow', 'seo_meta_noai']);
         })
         .select('setting_key', 'setting_value');
     });
@@ -76,7 +77,11 @@ router.get('/', async (req, res) => {
       event_require_customer_email: settingsObject.event_require_customer_email !== false,
       event_require_admin_email: settingsObject.event_require_admin_email !== false,
       event_require_event_date: settingsObject.event_require_event_date !== false,
-      event_require_expiration: settingsObject.event_require_expiration !== false
+      event_require_expiration: settingsObject.event_require_expiration !== false,
+      // SEO meta tag flags (safe to expose - these are intended for crawlers)
+      seo_meta_noindex: settingsObject.seo_meta_noindex === true,
+      seo_meta_nofollow: settingsObject.seo_meta_nofollow === true,
+      seo_meta_noai: settingsObject.seo_meta_noai === true
     };
 
     res.json(publicSettings);