Add multi-tenant cloud mode: self-serve purchase, credit metering, core-decoupling

Introduces RECAP_MODE=multi alongside single-mode self-host:
- Tenant auth + accounts (magic-link via System SMTP), per-tenant credit pool,
  anonymous trial minting with per-IP/-64 caps
- Self-serve Pro/Max purchase: inline Lightning (BTCPay) + card (Zaprite),
  prepaid 30-day periods, expiry-reminder emails
- Core-decoupling: relay owns cloud tier/expiry keyed by Recaps user-id
- SQLite (better-sqlite3) schema for multi-mode; filesystem unchanged for single
- StartOS actions/versions through 0.2.155

startos/versions/v0.2.49.ts

@@ -0,0 +1,12 @@
+import { VersionInfo } from '@start9labs/start-sdk'
+
+export const v_0_2_49 = VersionInfo.of({
+  version: '0.2.49:0',
+  releaseNotes: {
+    en_US: 'In-app buy page: clicking Upgrade now opens a Recap-styled tier-picker modal instead of redirecting to Keysat\'s hosted /buy/recap page. Tiers are pulled live from Keysat\'s policies API (so operator edits in Keysat admin show up without a Recap redeploy), rendered with marketing bullets + price + cadence suffix + featured-discount badges, and checkout opens in a new tab. After payment, the modal polls /api/license/poll/<invoiceId> every 4s and activates the issued license server-side once BTCPay settles. All five Upgrade buttons (toolbar, activation screen, license block, Pro upsell, etc.) point at the new modal.',
+  },
+  migrations: {
+    up: async ({ effects }) => {},
+    down: async ({ effects }) => {},
+  },
+})