Backups to master, replacement-VPS restore, broker proxy, multi-instance

Four features:

- Backup: lib/backup-sync.ts pushes the full settings table and firm
  credentials (the deliberate exception to "credentials never leave the
  machine") to the master's bearer-gated /api/instances/backup — every
  5 minutes when the content hash changed, within seconds of a settings
  or credential edit, and on the new backup-now command. Enabled by the
  master_backup_token setting.

- Restore: a dead VPS's replacement pulls the backup and adopts its
  uuid/name, so roster, payouts and card links carry on. Pre-boot via
  seed-settings.js --restore-from (setup-linux.sh prompts for it) or
  the Settings page's restore picker (lib/backup-restore.ts). Stop the
  old machine first; the master 409s a live-name rename.

- Proxy: the proxy_url setting routes BROKER traffic only — TopstepX
  REST + SignalR hub, Tradovate REST + websocket, Yahoo quotes — via
  lib/outbound-proxy.ts (axios agents, undici dispatcher, ws agent).
  The master link, reporter, catalog and backup push stay direct, so a
  dead proxy cannot take down the control channel. Restart to apply.

- Multi-instance: AUTOFIRMER_DB moves the SQLite file so one checkout
  runs N instances; scripts/instances.json (per-device, gitignored)
  drives start-all/update-check, and add-instance.sh / remove-instance.sh
  manage the extra PM2 processes. Absent registry = single-instance
  behavior, unchanged. Instance 1 keeps port 3000 for the clicker and
  extension.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/api/settings/route.ts

@@ -1,7 +1,8 @@
 import { NextRequest, NextResponse } from 'next/server';
 import { getSetting, setSetting } from '@/lib/db';
+import { scheduleBackupPush } from '@/lib/backup-sync';
 
-const VALID_KEYS = ['max_concurrent_accounts', 'tick_interval_seconds', 'master_dashboard_url', 'instance_name', 'trading_hours', 'twocaptcha_api_key', 'twocaptcha_proxy'] as const;
+const VALID_KEYS = ['max_concurrent_accounts', 'tick_interval_seconds', 'master_dashboard_url', 'instance_name', 'trading_hours', 'twocaptcha_api_key', 'twocaptcha_proxy', 'master_backup_token', 'proxy_url'] as const;
 type SettingKey = typeof VALID_KEYS[number];
 
 export async function GET() {
@@ -12,6 +13,8 @@ export async function GET() {
     // Read-only on purpose (not in VALID_KEYS): the master issues this uuid,
     // and editing it by hand would detach the instance from its person.
     result.instance_id = getSetting('instance_id');
+    result.backup_last_push_at = getSetting('backup_last_push_at');
+    result.backup_last_error = getSetting('backup_last_error');
     return NextResponse.json(result);
 }
 
@@ -27,6 +30,10 @@ export async function PATCH(req: NextRequest) {
             }
         }
 
+        // The edit should reach the master's backup within seconds, not at the
+        // next poll.
+        scheduleBackupPush();
+
         return NextResponse.json({ ok: true });
     } catch (err: any) {
         return NextResponse.json({ error: err?.message ?? 'Failed to save settings' }, { status: 500 });