fix: multiple production issues with PostgreSQL and connection handling

- Fix trust proxy to use specific values instead of permissive 'true'
- Fix clear old notifications to use database-agnostic date calculation
- Fix database size check to support both PostgreSQL and SQLite
- Add caching and better error handling for session timeout queries
- Add query timeout to prevent hanging connections
- Improve JSON parsing error handling for setting values

These fixes address:
- ERR_ERL_PERMISSIVE_TRUST_PROXY warning
- PostgreSQL datetime function errors
- ENOENT errors looking for SQLite file in PostgreSQL deployment
- Connection terminated errors for session timeout checks

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

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

backend/src/routes/adminSystem.js

@@ -35,14 +35,30 @@ router.get('/version', adminAuth, async (req, res) => {
 // Get comprehensive system status
 router.get('/status', adminAuth, async (req, res) => {
   try {
-    // Database size
-    const dbPath = path.join(__dirname, '../../data/photo_sharing.db');
+    // Database size - check if PostgreSQL or SQLite
     let dbSize = 0;
-    try {
-      const stats = await fs.stat(dbPath);
-      dbSize = stats.size;
-    } catch (error) {
-      console.error('Error getting database size:', error);
+    const dbClient = process.env.DATABASE_CLIENT || 'sqlite3';
+    
+    if (dbClient === 'pg') {
+      // PostgreSQL - query database size
+      try {
+        const dbName = process.env.DB_NAME || 'picpeak';
+        const result = await db.raw(`
+          SELECT pg_database_size(?) as size
+        `, [dbName]);
+        dbSize = result.rows[0]?.size || 0;
+      } catch (error) {
+        console.error('Error getting PostgreSQL database size:', error);
+      }
+    } else {
+      // SQLite - check file size
+      const dbPath = path.join(__dirname, '../../data/photo_sharing.db');
+      try {
+        const stats = await fs.stat(dbPath);
+        dbSize = stats.size;
+      } catch (error) {
+        console.error('Error getting SQLite database size:', error);
+      }
     }
 
     // Count various entities