Implement banking system features and enhancements

- Added banking mode with checking, savings, and charity accounts, including auto-split options for income.
- Introduced banking transaction management, including transfers and charity outflows.
- Updated family settings to allow configuration of banking features and interest rates.
- Enhanced data export functionality to include bank transactions.
- Improved user interface to display banking information and donation goals.
- Updated documentation to reflect new banking features and settings.

api/bank_set_donation_goal.php

@@ -0,0 +1,50 @@
+<?php
+
+require_once __DIR__ . '/../includes/api_bootstrap.php';
+require_once __DIR__ . '/../includes/family_settings.php';
+
+if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
+    sendJson(['success' => false, 'error' => 'Method not allowed'], 405);
+}
+
+$people = migrateAllPeople(normalizePeopleList(readJsonFile('people.json')));
+$actor = requireActivePerson($people);
+$settings = loadFamilySettings();
+if (empty($settings['banking_enabled'])) {
+    sendJson(['success' => false, 'error' => 'Banking mode is not enabled'], 400);
+}
+
+$body = readJsonBody();
+$goalRaw = $body['goal_monthly'] ?? null;
+if (!is_numeric($goalRaw)) {
+    sendJson(['success' => false, 'error' => 'goal_monthly must be numeric'], 400);
+}
+$goal = round((float) $goalRaw, 2);
+if ($goal < 0) {
+    sendJson(['success' => false, 'error' => 'goal_monthly must be >= 0'], 400);
+}
+$targetPersonId = trim((string) ($body['person_id'] ?? ''));
+$actorId = (string) ($actor['id'] ?? '');
+$isHoh = (($actor['role'] ?? '') === ROLE_HEAD) && isHohVerified();
+if ($targetPersonId === '') {
+    $targetPersonId = $actorId;
+}
+if (!$isHoh && $targetPersonId !== $actorId) {
+    sendJson(['success' => false, 'error' => 'Only verified Head of household can set goals for others'], 403);
+}
+
+$idx = null;
+foreach ($people as $i => $p) {
+    if (($p['id'] ?? '') === $targetPersonId) {
+        $idx = $i;
+        break;
+    }
+}
+if ($idx === null) {
+    sendJson(['success' => false, 'error' => 'Person not found'], 404);
+}
+$people[$idx]['donation_goal_monthly'] = $goal;
+if (!writeJsonFile('people.json', $people)) {
+    sendJson(['success' => false, 'error' => 'Failed to save goal'], 500);
+}
+sendJson(['success' => true, 'person' => $people[$idx]]);