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/v0.2.119.ts

@@ -0,0 +1,13 @@
+import { VersionInfo } from '@start9labs/start-sdk'
+
+export const v_0_2_119 = VersionInfo.of({
+  version: '0.2.119:0',
+  releaseNotes: {
+    en_US:
+      "Remove Phase-1-bugfix diagnostics now that buy → BTCPay → webhook → relay pool → display flow is verified end-to-end. Drops the /api/credits/diagnose endpoint and the outbound-identity log line from /api/credits/buy. The actual fix from v0.2.117 (per-user identity routing in relayHeaders) stays; this is just cleanup. Root cause of the Pro-tenant credit-not-incrementing bug turned out to be two-part: (1) Recaps was sending the operator's identity instead of the tenant's — fixed in v0.2.117; (2) the BTCPay webhook URL was still pointed at the old relay tunnel (relay.keysat.xyz) instead of the new one (relay.recaps.cc) — operator fixed via the relay's Set BTCPay Connection action.",
+  },
+  migrations: {
+    up: async ({ effects }) => {},
+    down: async ({ effects }) => {},
+  },
+})