Add comprehensive recurring payments system with scheduling

- Add RecurringPayment model with flexible scheduling options
- Implement node-cron based scheduler for payment processing
- Create API endpoints for CRUD operations on recurring payments
- Add recurring payments management UI with create/edit forms
- Integrate scheduler initialization in hooks.server.ts
- Enhance payments/add form with progressive enhancement
- Add recurring payments button to main dashboard
- Improve server-side rendering for better performance

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

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

src/routes/api/cospend/recurring-payments/cron-execute/+server.ts

@@ -0,0 +1,124 @@
+import type { RequestHandler } from '@sveltejs/kit';
+import { RecurringPayment } from '../../../../../models/RecurringPayment';
+import { Payment } from '../../../../../models/Payment';
+import { PaymentSplit } from '../../../../../models/PaymentSplit';
+import { dbConnect, dbDisconnect } from '../../../../../utils/db';
+import { error, json } from '@sveltejs/kit';
+import { calculateNextExecutionDate } from '../../../../../lib/utils/recurring';
+
+// This endpoint is designed to be called by a cron job or external scheduler
+// It processes all recurring payments that are due for execution
+export const POST: RequestHandler = async ({ request }) => {
+  // Optional: Add basic authentication or API key validation here
+  const authHeader = request.headers.get('authorization');
+  const expectedToken = process.env.CRON_API_TOKEN;
+  
+  if (expectedToken && authHeader !== `Bearer ${expectedToken}`) {
+    throw error(401, 'Unauthorized');
+  }
+
+  await dbConnect();
+  
+  try {
+    const now = new Date();
+    console.log(`[Cron] Starting recurring payments processing at ${now.toISOString()}`);
+    
+    // Find all active recurring payments that are due
+    const duePayments = await RecurringPayment.find({
+      isActive: true,
+      nextExecutionDate: { $lte: now },
+      $or: [
+        { endDate: { $exists: false } },
+        { endDate: null },
+        { endDate: { $gte: now } }
+      ]
+    });
+
+    console.log(`[Cron] Found ${duePayments.length} due recurring payments`);
+
+    const results = [];
+    let successCount = 0;
+    let failureCount = 0;
+
+    for (const recurringPayment of duePayments) {
+      try {
+        console.log(`[Cron] Processing recurring payment: ${recurringPayment.title} (${recurringPayment._id})`);
+
+        // Create the payment
+        const payment = await Payment.create({
+          title: `${recurringPayment.title} (Auto)`,
+          description: `Automatically generated from recurring payment: ${recurringPayment.description || 'No description'}`,
+          amount: recurringPayment.amount,
+          currency: recurringPayment.currency,
+          paidBy: recurringPayment.paidBy,
+          date: now,
+          category: recurringPayment.category,
+          splitMethod: recurringPayment.splitMethod,
+          createdBy: recurringPayment.createdBy
+        });
+
+        // Create payment splits
+        const splitPromises = recurringPayment.splits.map((split) => {
+          return PaymentSplit.create({
+            paymentId: payment._id,
+            username: split.username,
+            amount: split.amount,
+            proportion: split.proportion,
+            personalAmount: split.personalAmount
+          });
+        });
+
+        await Promise.all(splitPromises);
+
+        // Calculate next execution date
+        const nextExecutionDate = calculateNextExecutionDate(recurringPayment, now);
+
+        // Update the recurring payment
+        await RecurringPayment.findByIdAndUpdate(recurringPayment._id, {
+          lastExecutionDate: now,
+          nextExecutionDate: nextExecutionDate
+        });
+
+        successCount++;
+        results.push({
+          recurringPaymentId: recurringPayment._id,
+          paymentId: payment._id,
+          title: recurringPayment.title,
+          amount: recurringPayment.amount,
+          nextExecution: nextExecutionDate,
+          success: true
+        });
+
+        console.log(`[Cron] Successfully processed: ${recurringPayment.title}, next execution: ${nextExecutionDate.toISOString()}`);
+
+      } catch (paymentError) {
+        console.error(`[Cron] Error processing recurring payment ${recurringPayment._id}:`, paymentError);
+        failureCount++;
+        results.push({
+          recurringPaymentId: recurringPayment._id,
+          title: recurringPayment.title,
+          amount: recurringPayment.amount,
+          success: false,
+          error: paymentError instanceof Error ? paymentError.message : 'Unknown error'
+        });
+      }
+    }
+
+    console.log(`[Cron] Completed processing. Success: ${successCount}, Failures: ${failureCount}`);
+
+    return json({ 
+      success: true,
+      timestamp: now.toISOString(),
+      processed: duePayments.length,
+      successful: successCount,
+      failed: failureCount,
+      results: results
+    });
+
+  } catch (e) {
+    console.error('[Cron] Error executing recurring payments:', e);
+    throw error(500, 'Failed to execute recurring payments');
+  } finally {
+    await dbDisconnect();
+  }
+};