Fix: Transaction Sync Issues & Enhanced Debugging (#632)

* Fix mobile app to fetch all transactions with pagination

The mobile app was only fetching 25 transactions per account because:
1. TransactionsService didn't pass pagination parameters to the API
2. The backend defaults to 25 records per page when no per_page is specified
3. SyncService didn't implement pagination to fetch all pages

Changes:
- Updated TransactionsService.getTransactions() to accept page and perPage parameters
- Modified the method to extract and return pagination metadata from API response
- Updated SyncService.syncFromServer() to fetch all pages (up to 100 per page)
- Added pagination loop to continue fetching until all pages are retrieved
- Enhanced logging to show pagination progress

This ensures users see all their transactions in the mobile app, not just the first 25.

* Add clear local data feature and enhanced sync logging

Added features:
1. Clear Local Data button in Settings
   - Allows users to clear all cached transactions and accounts
   - Shows confirmation dialog before clearing
   - Displays success/error feedback

2. Enhanced sync logging for debugging
   - Added detailed logs in syncFromServer to track pagination
   - Shows page-by-page progress with transaction counts
   - Logs pagination metadata (total pages, total count, etc.)
   - Tracks upsert progress every 50 transactions
   - Added clear section markers for easier log reading

3. Simplified upsertTransactionFromServer logging
   - Removed verbose debug logs to reduce noise
   - Keeps only essential error/warning logs

This will help users troubleshoot sync issues by:
- Clearing stale data and forcing a fresh sync
- Providing detailed logs to identify where sync might fail

* Fix transaction accountId parsing from API response

The mobile app was only showing 25 transactions per account because:
- The backend API returns account info in nested format: {"account": {"id": "xxx"}}
- The mobile Transaction model expected flat format: {"account_id": "xxx"}
- When parsing, accountId was always empty, so database queries by account_id returned incomplete results

Changes:
1. Updated Transaction.fromJson to handle both formats:
   - New format: {"account": {"id": "xxx", "name": "..."}}
   - Old format: {"account_id": "xxx"} (for backward compatibility)

2. Fixed classification/nature field parsing:
   - Backend sends "classification" field (income/expense)
   - Mobile uses "nature" field
   - Now handles both fields correctly

3. Added debug logging to identify empty accountId issues:
   - Logs first transaction's accountId when syncing
   - Counts and warns about transactions with empty accountId
   - Shows critical errors when trying to save with empty accountId

This ensures all transactions from the server are correctly associated with their accounts in the local database.

---------

Co-authored-by: Claude <noreply@anthropic.com>

mobile/lib/models/transaction.dart

@@ -20,14 +20,33 @@ class Transaction {
   });
 
   factory Transaction.fromJson(Map<String, dynamic> json) {
+    // Handle both API formats:
+    // 1. New format: {"account": {"id": "xxx", "name": "..."}}
+    // 2. Old format: {"account_id": "xxx"}
+    String accountId = '';
+    if (json['account'] != null && json['account'] is Map) {
+      accountId = json['account']['id']?.toString() ?? '';
+    } else if (json['account_id'] != null) {
+      accountId = json['account_id']?.toString() ?? '';
+    }
+
+    // Handle classification (from backend) or nature (from mobile)
+    String nature = 'expense';
+    if (json['classification'] != null) {
+      final classification = json['classification']?.toString().toLowerCase() ?? '';
+      nature = classification == 'income' ? 'income' : 'expense';
+    } else if (json['nature'] != null) {
+      nature = json['nature']?.toString() ?? 'expense';
+    }
+
     return Transaction(
       id: json['id']?.toString(),
-      accountId: json['account_id']?.toString() ?? '',
+      accountId: accountId,
       name: json['name']?.toString() ?? '',
       date: json['date']?.toString() ?? '',
       amount: json['amount']?.toString() ?? '0',
       currency: json['currency']?.toString() ?? '',
-      nature: json['nature']?.toString() ?? 'expense',
+      nature: nature,
       notes: json['notes']?.toString(),
     );
   }