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

server/package.json

@@ -11,8 +11,11 @@
     "@anthropic-ai/sdk": "^0.95.0",
     "@google/genai": "^1.41.0",
     "@keysat/licensing-client": "file:../vendor/keysat-licensing-client",
+    "better-sqlite3": "^11.5.0",
     "cors": "^2.8.5",
+    "cookie": "^1.0.1",
     "express": "^4.21.0",
+    "nodemailer": "^6.9.16",
     "openai": "^6.37.0"
   }
 }