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/v0.2.115.ts

@@ -0,0 +1,13 @@
+import { VersionInfo } from '@start9labs/start-sdk'
+
+export const v_0_2_115 = VersionInfo.of({
+  version: '0.2.115:0',
+  releaseNotes: {
+    en_US:
+      "Better payment-confirmed moment for credit purchases. Instead of immediately closing the buy modal and tossing a 'credits added' toast in the corner, the modal now transitions to a centered success view: a green pop-in checkmark, a brief radial sparkle burst (✨ ⚡ ⭐ pure CSS, no library), 'Payment confirmed' headline, and 'N Recap credits added to your balance' subtext. Auto-closes after 2.8s; Done button closes sooner. Gives the buyer a clear visual beat that the payment actually landed before the UI moves on.",
+  },
+  migrations: {
+    up: async ({ effects }) => {},
+    down: async ({ effects }) => {},
+  },
+})