fix: comprehensive PostgreSQL/SQLite compatibility fixes

Critical fixes for database compatibility issues:

INSERT operations:
- Fix all INSERT queries to use .returning('id')
- Handle both PostgreSQL (returns objects) and SQLite (returns IDs)
- Fixed in: events.js, adminArchives.js, adminEvents-enhanced.js, create-test-event.js

Date operations:
- Replace SQLite-specific db.raw("datetime('now', '+30 days')")
- Use JavaScript Date objects for cross-database compatibility
- Fixed in: adminArchives.js

Database utilities:
- Add dbCompat.js utility for handling database differences
- Provides consistent API for inserts, dates, booleans, and DB-specific operations
- Centralized database compatibility logic

Migration:
- Add migration 023 documenting PostgreSQL compatibility requirements
- Ensures future developers are aware of compatibility needs

This resolves all 'not iterable' errors and ensures the application
works correctly with both PostgreSQL (production) and SQLite (development).

backend/src/routes/adminArchives.js

@@ -211,12 +211,14 @@ router.post('/:id/restore', adminAuth, async (req, res) => {
                   categoriesMap.set(categoryName, existingCategory.id);
                 } else {
                   // Create the category if it doesn't exist
-                  const [newCategoryId] = await db('photo_categories').insert({
+                  const insertResult = await db('photo_categories').insert({
                     event_id: archive.id,
                     name: categoryName,
                     slug: categoryName.toLowerCase().replace(/[^a-z0-9]/g, '-'),
                     created_at: new Date()
-                  });
+                  }).returning('id');
+                  
+                  const newCategoryId = insertResult[0]?.id || insertResult[0];
                   categoriesMap.set(categoryName, newCategoryId);
                 }
               }
@@ -266,6 +268,9 @@ router.post('/:id/restore', adminAuth, async (req, res) => {
     }
     
     // Update event status
+    const thirtyDaysFromNow = new Date();
+    thirtyDaysFromNow.setDate(thirtyDaysFromNow.getDate() + 30);
+    
     await db('events')
       .where('id', req.params.id)
       .update({
@@ -273,7 +278,7 @@ router.post('/:id/restore', adminAuth, async (req, res) => {
         is_active: true,
         archive_path: null,
         archived_at: null,
-        expires_at: db.raw("datetime('now', '+30 days')") // Reset expiration
+        expires_at: thirtyDaysFromNow.toISOString() // Reset expiration - works on both DBs
       });
 
     // Log activity

backend/src/routes/adminEvents-enhanced.js

@@ -83,7 +83,7 @@ router.post('/', adminAuth, [
     await fs.mkdir(path.join(eventPath, 'individual'), { recursive: true });
     
     // Insert into database
-    const [eventId] = await db('events').insert({
+    const insertResult = await db('events').insert({
       slug,
       event_type,
       event_name,
@@ -99,7 +99,10 @@ router.post('/', adminAuth, [
       created_at: new Date().toISOString(),
       allow_user_uploads,
       upload_category_id
-    });
+    }).returning('id');
+    
+    // Handle both PostgreSQL (returns array of objects) and SQLite (returns array of IDs)
+    const eventId = insertResult[0]?.id || insertResult[0];
     
     // Log activity
     await logActivity('event_created', 

backend/src/routes/events.js

@@ -64,7 +64,7 @@ router.post('/', adminAuth, [
     await fs.mkdir(path.join(eventPath, 'individual'), { recursive: true });
     
     // Insert into database
-    const [eventId] = await db('events').insert({
+    const insertResult = await db('events').insert({
       slug,
       event_type,
       event_name,
@@ -76,7 +76,10 @@ router.post('/', adminAuth, [
       color_theme,
       share_link: shareLink,
       expires_at
-    });
+    }).returning('id');
+    
+    // Handle both PostgreSQL (returns array of objects) and SQLite (returns array of IDs)
+    const eventId = insertResult[0]?.id || insertResult[0];
     
     // Queue creation email
     const { queueEmail } = require('../services/emailProcessor');